^>;^. 
^^u 


LIBRARY     OF 


1685-1056 


ENTOMOLOGY 

FOLSOM 


DESCRIPTION  OF  FRONTISPIECE. 
Protective  Mimicry  among  Butterflies. 

Fig.  I. — Hcliconius  ei'crate,  one  of  the  Helicoiiiinx,  wliicli  are  iiaturally  iiiiniuiic  from 
the  attacks  of  birds.     From  Brazil. 

Fig.  2. — Perhybris  pyrrha,  female  (Pierinas),  which  is  edible  by  birds  but  ))robably 
secures  immunity  by  means  of  its  resembiaiice  to  such  species  as  No.  i  or  No.  4. 
Brazil. 

FiG.  3. — Perhybris  pyrrha,  male,  to  show  the  colorational  basis  from  which  the 
mimetic  pattern  of  the   female  has  been   developed;   under  surface  on   right.      Brazil. 

Fig.  4. — Mechanitis  lysimnia  (.Ithomiins),  naturally  immune,  but  nevertheless 
sharing  a  common  color  pattern  with  Heliconiinas   (No.   i).      Brazil. 

Fig.  5. — Papilio  merope,  male,  having  three  forms  of  females  ( Nos.  7,  9  and  11), 
which  mimic,  respectively,  three  species  of  Danainse  (Nos.  6,  8  and  10).  South 
Africa. 

Fig.  6. — Danais  chrysippus,  irnmune,  mimicked  by  No.  7.     South  Africa. 

Fig.  7. — Papilio  merope,  female,  which  mimics  No.   6.     South  Africa. 

Fig.  8. — Amauris  niavius,  "  model  "  of  No.  9.     South   .Africa. 

Fig.  9. — Papilio   merope,   female,   "  mimic  "  of   No.   8.     South   Africa. 

Fig.   10. — Amauris  ccheria,  "model"  of  No.    11.     South  Africa. 

Fig.   II. — Papilio  merope,  female,  "mimic"  of  No.   10.     South  Africa. 

The  figures  are  about  one  half  the  natural  size.  Compiled,  largely  from  Trimen 
and  Weismann. 


-llSfi.Jt    ill. 


.ttS£-iH 

il    Isrioilfiiofos    arfJ    wofte    at    .sli..  .r.  .oi'^ 

1    .  aDBlirjg  labritx   ;h9iji'        '  '  " 

rtfl     .sfitiminf     vdeiijiBii 

its    8    ,d    .e.  /  ,fn    ifDirfw 

.,,ji7-l/ 

ii^A   dloofe 
r.jn>A   riJiM- 

.Kjiri 

'  '• ;  i/  [-jbom  "  .nif. 


ENTOMOLOGY 

WITH  SPECIAL  REFERENCE  TO 

ITS    BIOLOGICAL  AND    ECONOMIC  ASPECTS 


JUSTUS     WATSON     FOLSOM.    Sc.D.    (Harvard) 

INSTKICTOR    IN    ENTOMOLOGY    AT    THE    UNIVEKSH  Y    OF    ILLINOIS 


lUitb  jfive  plates  (One  ColoreD) 


PHILADELPHIA  : 
BLAKISTON'S   SON  &    CO. 

IOI2  WALNUT   STREET 
1906 


Copyright,  1906,  by  P.  Blakiston's  Son  &  Co. 


PREFACE 

This  book  gives  a  comprehensive  and  concise  account  of 
insects.  Though  planned  primarily  for  the  student,  it  is  in- 
tended also  for  the  general  reader. 

The  book  was  written  in  an  effort  to  meet  the  growing 
demand  for  a  biological  treatment  of  entomology. 

The  existence  of  several  excellent  works  on  the  classification 
of  insects  (notably  Comstock's  Manual,  Kellogg's  American 
Insects  and  Sharp's  Insects)  has  enabled  the  author  to  omit 
the  multitudinous  details  of  classification  and  to  introduce 
much  material  that  hitherto  has  not  appeared  in  text-books. 

As  a  rule,  only  the  commonest  kinds  of  insects  are  referred 
to  in  the  text,  in  order  that  the  reader  may  easily  use  the  text 
as  a  guide  to  personal  observation. 

All  the  illustrations  have  been  prepared  by  the  author,  and 
such  as  have  been  copied  from  other  works  are  duly  credited. 

To  Dr.  S.  A.  Forbes  the  author  is  especially  indebted  for 
the  use  of  literature,  specimens  and  drawings  belonging  to  the 
Illinois  State  Laboratory  of  Natural  History. 

Permission  to  copy  several  illustrations  from  Government 
publications  was  received  from  Dr.  L.  O.  Howard,  Chief  of 
the  Bureau  of  Entomology;  Dr.  C.  Hart  Merriam,  Chief  of 
the  Division  of  Biological  Survey,  and  Dr.  Charles  D.  Walcott, 
Director  of  the  U.  S.  Geological  Survey.  Several  desired 
books  were  obtained  from  F.  M.  Webster,  of  the  Bureau  of 
Entomology. 

Acknowledgments  for  the  use  of  figures  are  due  also  to 
Dr.  E.  P.  Felt,  State  Entomologist  of  New  York;  Dr.  E.  A. 
Birge,  Director  of  the  Wisconsin  Geological  and  Natural  His- 
tory Survey;  Prof.  E.  L.  Mark  and  Prof.  Roland  Thaxter, 
of  Harvard  University ;  Prof.  J.  H.  Comstock  of  Cornell  Uni- 
versitv;  Prof.  C.  W.  Woodworth  of  the  Universitv  of  Cali- 


VI  PREFACE 

fornia ;  Prof.  G.  Macloskie  of  Princeton  University ;  Prof.  \V. 
A.  Locy  of  Northwestern  University ;  Prof.  J.  G.  Needham 
of  Lake  Forest  University ;  Dr.  S.  H.  Scnckler  of  Cambridge, 
Mass. ;  Dr.  George  Dimmock  of  SpringfiekJ,  Mass. ;  Dr. 
Howard  Ayers  of  Cincinnati,  Ohio ;  Dr.  W.  M.  Wheeler  of 
the  American  Museum  of  Natural  History,  New  York  City; 
Dr.  W.  L.  Tower  of  the  University  of  Chicago ;  Dr.  A.  G. 
Mayer,  Director  of  the  Marine  Biological  Laboratory,  Tortu- 
gas,  Fla. ;  James  H.  Emerton  of  Boston,  Mass. ;  Dr.  and  Mrs. 
G.  W.  Peckham  of  Milwaukee,  Wis. ;  Dr.  Henry  C.  McCook 
of  Devon,  Penn. ;  Dr.  William  Trelease,  Director  of  the  Mis- 
souri Botanical  Garden ;  Dr.  Henry  Skinner,  as  editor  of  "  En- 
tomological News  "  ;  the  editors  of  "  The  American  Natural- 
ist " ;  and  W.  Saville-Kent,  of  Wallington,  England. 

Acknowledgments  are  further  due  to  the  Boston  Society  of 
Natural  History,  the  American  Philosophical  Society  and  the 
Academy  of  Science  of  St.  Louis. 

Courteous  permission  to  use  certain  figures  was  given  also 
by  The  Macmillan  Co. ;  Henry  Holt  &  Co. ;  Ginn  &  Co. ;  Prof. 
Carl  Chun  of  Leipzig;  F.  Diimmler  of  Berlin,  publisher  of 
Kolbe's  Einfiihrung;  and  Gustav  Fischer  of  Jena,  publisher  of 
Hertwig's  Lehrbuch  and  Lang's  Lehrbuch. 


CONTENTS 

Chapter  Page 

I.  Classification i 

II.  Anatomy  and  Physiology  27 

III.  Development  146 

IV.  Adaptations  of  Aquatic  Insects 184 

\'.  Color  and  Coloration   193 

\' I.  Adaptive  Coloration 216 

VII.  Origin  of  Adaptations  and  of  Species 237 

VIII.  Insects  in  Relation  to  Plants 252 

IX.  Insects  in  Relation  to  Other  Animals 276 

X.  Interrelations  of  Insects   307 

XL  Insect  Behavior    345 

XII.  Distribution    366 

XIII.  Insects  in  Relation  to  Man  393 

Literature 409 

Index 467 


ENTOMOLOGY 


CHAPTER    I 


CLASSIFICATION 


At  the  outset  it  is  essential  to  know  where  insects  stand  in 
relation  to  other  animals. 

Arthropoda. — Comparing  an  insect,  a  centipede  and  a 
crayfish  with  one  another,  they  are  found  to  have  certain 
fundamental  characters  in  common.  All  are  bilaterally  sym- 
metrical, are  composed  of  a  linear  series  of  rings,  or  segments, 
bearing  paired,  jointed  appendages,  and  have  an  external 
skeleton,  consisting  largely  of  a  peculiar  substance  known  as 
chitin. 

If  the  necessary  dissections  are  made,  it  can  be  seen  that 
in  each  of  these  types  the  alimentary  canal  is  axial  in  position : 


Diagram  to  express  the  fundamental  structure  of  an  arthropod,  a,  antenna;  al, 
alimentary  canal;  b,  brain;  d,  dorsal  vessel;  c.v,  exoskeleton;  /,  limb;  n,  nerve  chain; 
s,   suboesophageal   ganglion. — After   Schmeil. 


above  it  extends  the  dorsal  blood  vessel  and  below  lies  the 
ventral  ladder-like  series  of  segmental  ganglia  and  paired 
nerve  cords,  or  commissures ;  between  the  commissures  that 
connect  the  brain  and  the  suboesophageal  ganglion  passes  the 
oesophagus.     These    relations    appear    in    Figs,     i    and    163. 


ENTOMOLOGY 


Fig 


Furthermore,  the  sexes  are  ahnost  invariably  separate  and  the 
primary  sexual  organs  consist  of  a  single  pair. 

No  animals  but  arthropods  have  all  these  characters,  though 
the  segmented  worms,  or  annelids,  have  some  of  them — for 
example  the  segmentation,  dorsal  heart  and  ventral  nervous 

chain.  On  account  of  these 
correspondences  and  for  other 
weighty  reasons  it  is  believed 
that  arthropods  have  de- 
scended from  annelid-like  an- 
cestors. Annelids,  however, 
as  contrasted  with  arthropods, 
have  segments  that  are  essen- 
tially alike,  have  no  external 
skeleton  and  never  have 
paired  limbs  that  are  jointed. 
Classes  of  Arthropoda. — 
Excepting  the  king-crab,  tri- 
lobites  and  a  few  other  aber- 
rant forms  of  uncertain  posi- 
tion, the  members  of  the 
series,  or  phylum,  Arthropoda 
fall  into  six  distinct  classes, 
namely,  Crustacea,  Arach- 
nida,  Malacopoda,  Diplopoda, 
Chilopoda  and  I  n  s  e  c  t  a  . 
These  classes  are  character- 
ized as  follows : 

Crustacea. — Aquatic,  as  a 
rule.  Head  and  thorax  often  united  into  a  cephalothorax. 
Numerous  paired  appendages,  typically  biramous  (Y-shaped)  ; 
abdominal  limbs  often  present.  Two  pairs  of  antennae.  Res- 
piration branchial  (by  means  of  gills)  or  cutaneous  (directly 
through  the  skin).  The  exoskeleton  contains  carbonate  and 
phosphate  of  lime  in  addition  to  chitin.  Example,  cray- 
fish. 


scorpion,    Buthus.     Natural    size. 


CLASSIFICATION 


3 


Arachnida. — Terrestrial.  Usually  two  re,Q'ions,  ccphalo- 
thorax  and  abdomen;  thoui^'h  xarioiis  Acarina  lia\c  but  cjiie 
and  Solpngida  have  all  three — head,  thorax  and  abdomen. 
Ceplialothorax  unsegmented,  bearing  two  pairs  of  oral  append- 


FlG.  3. 


Pcripafus  cafensis.     Natural   size. — After  Moseley. 


Fic 


ages  and  four  pairs  of  legs.  Abdomen  segmented  or  not, 
limbless.  Respiration  tracheal,  by  means  of  book-leaf  tra- 
cheae, tubular  tracheae,  or  both ;  stigmata  almost  always  abdom- 
inal, at  most  four  pairs.  Heart  abdominal  in  position. 
Example,  Buthiis  (Fig.  2). 

Malacopoda.  —  Terrestrial. 
Vermiform  (worm-like),  unseg- 
mented externally.  One  pair  of 
antennae,  a  pair  of  jaws  and  a 
pair  of  oral  slime  papillae.  Legs 
numerous,  paired,  imperfectly 
segmented.  Respiration  by  means 
of  tubular  tracheae,  the  stigmata 
of  which  are  scattered  over  the 
surface  of  the  body.  Numerous 
nephridia  (excretory)  are  pres- 
ent and  these  are  arranged  seg- 
mentally  in  pairs.  Two  separate 
longitudinal  nerve  cords,  con- 
nected by  transverse  commissures, 
single  genus.  Pcripafus  (Fig.  3),  comprising  many  species. 

Diplopoda. — Terrestrial.  Two  regions,  head  and  body. 
Body  usually  cylindrical,  w'ith  numerous  segments,  most  of 
which  are  double  and  bear  two  pairs  of  short  limbs,  which  are 
inserted  near  the  median  ventral  line.     Eyes  simple,  antennae 


A    diplopod,    Spiroholus   marginatum 
Natural    size. 


Integument  delicate.     A 


ENTOMOLOGY 


Fig.  5. 


short,  mouth  parts  consisting  of  a  pair  of  mandibles  and  a 
compound  plate,  or  gnathochilarium.  Genital  openings  sepa- 
rate, anterior  in  position  (on  the  second  segment  of  the  body). 
Example,  Spiroholus  (Fig.  4). 

Chilopoda. — Terrestrial.  Two  regions,  head  and  body. 
Body  long  and  flattened,  with  numerous  segments,  each  of 
which  bears  a  pair  of  long  six- 
or  seven-jointed  limbs,  which  are 
not  inserted  near  the  median  line. 
Eyes  simple  and  numerous  (ag- 
glomerate in  Scutigcra) ,  antennae 
long.  A  pair  of  mandibles  and 
two  pairs  of  maxilla;.  A  single 
genital  opening,  on  the  preanal 
segment.     Example,  Scolopcndva 

(I^^ig-  5)- 

Insecta  (Hexapoda) .  —  Pri- 
marily terrestrial.  Three  distinct 
regions — head,  thorax  and  abdo- 
men. Head  with  a  pair  of  com- 
pound eyes  in  most  adults,  one 
pair  of  antennas  and  three  pairs 
of  mouth  parts — mandibles,  max- 
illae and  labium — besides  which 
a  hypopharynx,  or  tongue,  is 
present.  Thorax  with  a  pair  of 
legs  on  each  of  its  three  segments 
and  usually  a  pair  of  wings  on 
each  of  the  posterior  two  seg- 
ments ;  though  there  may  be  only 
one  pair  of  wings  (as  in  Diptera 
and  male  Coccid<T)  ;  the  pro- 
thorax  never  bears  wings.  Ab- 
domen typically  with  ten  seg- 
ments (seldom  more)  and  without  legs,  excepting  in  some 
larv.T    (as  those  of  Lepidoptera,  Tenthredinida?  and   Panor- 


A  centipede,  Scolopcndra  h 
About  two  thirds  the  maxi 
length. 


CLASSIFICATION  5 

pid;r)-  Stigmata  paired  and  segnientally  arranged.  A  meta- 
morphosis (direct  or  indirect)  occurs  except  in  Thysannra  and 
Collembola. 

Relationships. — The  interrelationships  of  the  classes  of 
Arthropoda  form  an  obscure  and  highly  debatable  subject. 

Crustacea  and  Insecta  agree  in  so  many  morphological 
details  that  their  resemblances  can  no  longer  ]je  dismissed  as 
results  of  a  vague  "  parallelism,"  or  "  convergence  ' '  of  devel- 
opment, but  are  inexplicable  except  in  terms  of  community  of 
origin,  as  Carpenter  has  lately  insisted. 

Arachnida  are  extremely  unlike  other  arthropods  but  find 
their  nearest  allies  among  Crustacea,  particularly  the  fossil 
forms  known  as  trilobites. 

Malacopoda,  as  represented  by  Pcripatus,  are  often  spoken 
of  as  bridging  the  gulf  that  separates  Insecta,  Chilopoda  and 
Diplopoda  from  Annelida.  Peripatus  indeed  resembles  the 
chsetopod  annelids  in  its  segmentally  arranged  nephridia, 
dermo-muscular  tube,  coxal  glands  and  soft  integument,  and 
resembles  the  three  other  classes  in  its  tracheae,  dorsal  vessel, 
lacunar  circulation,  mouth  parts  and  salivary  glands.  These 
resemblances,  however,  are  by  no  means  close,  and  Pcripatus 
does  not  form  a  direct  link  between  the  other  tracheate  arthro- 
pods and  the  annelid  stock,  but  is  best  regarded  as  an  offshoot 
from  the  base  of  the  arthropodan  stem. 

In  speaking  o'f  annelid  ancestors,  none  of  the  recent  annelids 
are  meant,  of  course,  but  reference  is  made  to  the  primordial 
stock  from  which  recent  annelids  themselves  have  been  de- 
rived. 

Though  Diplopoda  and  Chilopoda  have  long  been  grouped 
together  under  the  name  Myriopoda,  they  really  have  so  little 
in  common,  beyond  the  numerous  limb-bearing  segments  and 
the  characters  that  are  possessed  by  all  tracheate  arthropods, 
that  their  differences  entitle  them  to  rank  as  separate  classes. 
Chilopoda  as  a  whole  are  more  nearly  related  to  Insecta  than 
are  Diplopoda,  as  regards  segmentation,  mouth  parts,  tracheae, 
genital  openings  and  other  characters. 


ENTOMOLOGY 


ScolopcndrcUa,  now  placed  either  among  Diplopoda  or  else 
in  a  class  by  itself,  Symphyla,  presents  a  remarkable  combina- 


FiG.  6. 


Section  of  Scolopendrella  immacitlata.  b,  brain;  c,  coxal  gland;  /,  fore  intestine; 
li,  hind  intestine;  in,  mid  intestine;  n,  nerve  chain;  o,  opening  of  silk  gland;  od, 
oviduct;  oi',  ovary;  s,  silk  gland;   u,  urinary  tube. — After  Packard. 


tion  of  diplopodan  and  insectean  characters.  Scolopendrella 
(Fig.  6)  and  the  thysamiran  Cam  pod  ca  have  the  same  kind 
of  head,  with  its  long  moniliform  antennae,  and  agree  in  the 
general  structure  of  the  mouth  parts ; 
the  number  of  body  segments  is  nearly 
the  same,  the  legs  and  claws  are  essen- 
tially alike,  and  cerci  and  paired  abdom- 
inal stylets  are  present  in  the  two  genera, 
not  to  mention  the  correspondences  of 
internal  organization.  Indeed,  it  is 
highly  probable,  as  Packard  maintained, 
that  the  most  primitive  insects,  Thys- 
anura  (and  consecjuently  all  other  in- 
sects), originated  from  a  form  much  like 
Scolopendrella.  A  singular  thysanuran. 
Ana  ja  pyx  vcsiculosus  (Fig.  7),  has 
lately  been  discovered  by  Silvestri,  who 
regards  it  as  being  in  many  respects  the 
most  primitive  insect  known,  combining 
as  it  does  characters  of  Symphyla,  Diplo- 
poda and  Canipodea. 
The  following  diagram  (Fig.  8)  expresses  very  crudely  one 
view  as  to  the  annelid  origin  of  the  chief  classes  of  Arthro- 
poda. 


Anajapyx  vesiculosus. 
Length,  2  mm. — After 
Silvestri. 


CLASSIFICATION 


The  naturalness  of  the  phyhim  Arthropoda  has  been  ques- 
tioned by  Kingsley  and  Packard.  The  latter  author  recently 
divided  Arthropoda  into  five  independent  phyla,  holding  that 


Fig.  8. 

INSECTA 


CRUSTACEA 


ARACHNIDA 


CHILOPODA 
DIPLGPGDA 


MALACOPODA 
ANNELIDA 


Diagram   to   indicate   the   origin   of   Arthropoda. 


"  there  was  no  common  ancestor  of  the  Arthropoda  as  a 
whole,  and  that  the  group  is  a  polyphyletic  one."  This  icono- 
clastic view,  however,  by  emphasizing  unduly  the  structural 
differences  among  arthropods,  tends  to  conceal  the  many  deep- 
seated  resemblances  that  exist  between  the  classes  of  Arthro- 
poda. 

Carpenter,  in  a  most  sagacious  summary  of  the  whole  sub- 
ject of  arthropod  relationships,  has  recently  brought  together 
no  little  evidence  in  favor  of  a  revised  form  of  the  old  Miil- 
lerian  theory  of  crustacean  origins.  He  traces  all  the  classes 
of  Arthropoda  back  to  common  arthropodan  ancestors  with  a' 
definite  number  of  segments  and  distinctly  crustacean  in 
character;  then  traces  these  primitive  arthropods  back  to 
forms  like  the  nauplius  larva  of  Crustacea,  and  these  in  turn 


8 


ENTOMOLOGY 


to  a  hypothetical  form  Hke  the  trochosphere  larva  of  recent 
polychsete  annelids. 

Orders   of   Insects. — Linnaeus   arranged   insects   in   seven 
orders,  namely,  Coleoptera,  Hemiptera,  Lepidoptera,  Neurop- 

FiG.  9.  Fig.  10. 


Campodea.     Length, 
3   mm. 


Lepisma.     Length, 
10  mm. 


tera,  Hymenoptera,  Diptera  and  Aptera.  The  wingless  in- 
sects termed  Aptera  were  soon  found  to  belong  to  diverse 
orders  and  the  name  has  now  become  so  ambiguous  as  to  meet 
with  little  approbation. 

From  the  Linnjean  group  Hemiptera,  the  Orthoptera  were 
set  apart ;  the  old  order  Neuroptera,  a  heterogeneous  and 
unnatural  group,  has  been  split  into  several  distinct  orders, 
and  many  other  changes  in  the  classification  have  been  neces- 
sary. 

Without  entering  any  further  into  the  history  of  the  sub- 
ject, it  is  sufficient  to  say  that  increasing  discrimination  on  the 


CLASSIFICATION 


part  of  entomologists  has  been  followed  by  a  gradual  increase 
in  the  number  of  orders,  until  our  present  system  has  been 
attained. 

Owing  to  the   incomplete   condition  ^''''-  ^^• 

of  entomological  knowledge,  however, 
the  best  system  as  yet  proposed  is  but 
tentative  and  more  or  less  open  to 
objection.  The  most  competent  and 
widely  approved  classifications  are 
those  of  Brauer  and  Packard,  and 
the  system  here  adopted  is  essential!}- 
that  of  Brauer,  with  certain  important 
modifications  made  by  Packard. 

In  the  course  of  the  following  syn- 
opsis of  the  orders  of  insects  it  is 
necessary  to  use  some  terms,  as  nicfa- 
morphosis  and  thysannrifonii,  in  an- 
ticipation of  their  subsequent  defini- 
tion. 

I.  Thysanura. — No  metamorphosis. 
Mouth  parts  mandibulate,  either  free 
(ectognathous)  or  enclosed  in  the 
head  (entognathous).  Wings  inva- 
riably absent.  Thoracic  segments  simple  and  similar.  Ab- 
dominal segments  ten, 
with  two  to  eight  pairs 
of  rudimentary  limbs 
and  two  or  three  anal 
cerci.  Eyes  aggregate, 
compound  or  absent. 
Antennae  multiarticulate. 
Integument  thin.  Ex- 
amples, Cam  pod  ca  (Fig. 
9),  Japyx,  Machilis, 
Some  one  hundred  and  seventy-five  spe- 


The  snow  flea,  Acho- 
lics nivicola.  Length, 
mm. 


Fig 


IS   liorteiisis.     Lengt 


Lepisina  (Fig.  10), 
cies  are  known. 


lO 


ENTOMOLOGY 


2.  Collembola. — Xo  metamorphosis.  Mouth  parts  entog- 
nathous  and  typically  mandibulate,  with  occasional  secondary 
suctorial  modifications.  Wings  invariably  absent.  Thoracic 
segments  simple  and  similar  or  prothorax  reduced.  Body 
cylindrical  or  globular;  abdomen  with  six  segments.  Ventral 
tube  and  furcula  usually  present,  rarely  rudimentary.  Eyes 
ocelliform  or  absent.  Antennae  of  four  segments  in  most 
genera ;  five  or  six  in  a  few  genera.  Integument  delicate. 
Examples.  Achorutes  (Fig.  ii).  Sniinthurus  (Fig,  12). 
About  seven  hundred  species  have  been  described. 


Fig. 


Fig. 


Hemimcrus  falpoidcs. 
Length,  11.5  mm. — After 
Hansen. 


Schistocerca    americana.     Slightly    reduced. 


Under  the  term  Aptcrygota  ( Apterygogenea,  Brauer ; 
Synaptera,  Packard )  the  Thysanura  and  Collembola,  as  primi- 
tively wingless  insects,  are  conveniently  distinguished  from  all 
other  insects,  or  Pterygofa  ( Pterygogenea,  Brauer). 

3.  Orthoptera. — ^Metamorphosis  direct.  Mouth  parts  man- 
dibulate.  Wings  two  pairs  as  a  rule,  though  not  infrequently 
reduced  or  absent;  front  wings  coriaceous   (tegmina)  ;  hind 


CLASSIFICATION  I  I 

pair  membranous,  ample,  closely  reticulate,  plicate  along  the 
numerous  radiating  principal  veins.  Abdomen  with  ten  or 
eleven  segments.  Eight  families :  Forficulidas,  Hemimeridse 
(Fig.  13),  Blattida?,  MantidcC,  Phasmidae  (Fig.  240),  Acri- 
diidje  (Fig.  14),  Locustid;e,  Gryllicke.  Over  ten  thousand 
species  are  known. 

Some  authors  prefer  to  separate  ForficulidcX  from  Orthop- 
tera  as  a  distinct  order,  for  which  Brauer  and  Packard  pre- 
serve the  old  term  Dcrmaptera  of  Leach,  while  Comstock  uses 
Westwood's  term  Euplcxoptcra. 

Hemimerida?  consist  at  present  of  two  African  species 
whose  affinities  appear  to  lie  with  Forficulida.%  but  deserve 
further  study. 

4.  Platyptera. — Aletamorphosis  direct.  Mouth  parts  man- 
dibulate.  Wings,  if  present,  two  pairs,  delicate,  membranous, 
equal  or  hind  pair  smaller,  and  with  the  principal  veins  few 
and  simple.  Integument  usually  thin.  Nymphs  thysanuri- 
form.     Two  suborders. 

Suborder  Corrodentia. — Including  three  families,  as  fol- 
lows : 

Tcnnitidcc.  —  Eyes  facetted.  Antennje  9-31  jointed. 
Mouth  parts  prognathous  or  hypognathous.^  Prothorax 
large.  Wings  elongate,  alike,  membranous,  delicate,  with 
indefinite  reticulation  and  with  a  characteristic  basal  suture. 
Abdomen  elongate,  with  ten  segments  and  a  pair  of  short, 
two-jointed  anal  cerci.  Integument  delicate.  Social  in  habit. 
Example,  Tcniics  (Fig.  273).  Over  one  hundred  species  are 
known. 

Comstock  places  Termitid:e  in  an  order  by  themselves, 
Isoptera. 

Emhiidcc.  —  Eyes  facetted.  Antennae  15-32  jointed. 
Mouth  parts  prognathous.  Thorax  elongate,  prothorax  re- 
duced. Wings  (sometimes  absent)  elongate,  membranous, 
delicate,  with  few  and  feebly  developed  longitudinal  and  cross 
veins.     Abdomen  elongate,  with  ten  or  possibly  eleven  seg- 

^  Progiiatlioiis,  directed  forward;   liypognathoiis,  directed  downward. 


ENTOMOLOGY 


OHgotoma  michacU.      Length,    10.5   mm. 
McLachlan. 


ments,  and  a  pair  of  stout  biarticulate  cerci.  Integument  deli- 
cate. Not  social  in  habit.  Examples,  Emhia,  OHgotoma 
(Fig-.  15).     Some  twenty  species,  all  from  warm  climates. 

These  insects  are  most 
nearly  related  to  Termit- 
dse  and  Psocidje. 

Psocidcu.  —  Eyes  facet- 
ted. Antenn?e  13-50 
jointed.  Mouth  parts 
hypognathous.  Protho- 
rax  reduced.  Wings 
present,  rudimentary  or 
absent ;  front  pair  the 
larger;  veins  few  and  ir- 
regular. Abdomen  with 
nine  or  ten  segments  and 
no  cerci.  Integument  delicate.  Example,  Psociis  (Fig.  16). 
About  two  hundred  species. 

Comstock  raises  Psocidse  to  the  rank  of  an  order,  for  which 
he  employs,  in  a  new  sense,  Brauer's  term  Corrodentia. 

Suborder  Mallophaga. — Wingless  flattened  insects,  of  para- 
sitic habit.  Head  large.  Eyes  consisting  of  a  few  isolated 
ocelli  or  else  absent.  An- 
tennae 3-5  jointed.  Mouth 
parts  prognathous.  Pro- 
thorax  distinct ;  mesotho- 
rax  often  and  metathorax 
usually  transferred  to  the 
abdominal  region.  Ab- 
dominal segments  eight  to 
ten  in  number;  no  cerci.  Parasitic  upon  birds  and  a  few  mam- 
mals. Example,  Menopon  (Fig.  17).  More  than  fifteen 
hundred  species  have  been  described. 

Packard's  order  Platyptcra  originally  included  Perlid^e. 
Brauer's  order  Corrodentia  consisted  of  Termitidse,  Psocidse 
and  Mallophaga;  Perlidse  being  set  apart  as  an  order  {Plecop- 


PsocHS  zTHOSus.     Length,   5 


CLASSIFICATION 


13 


Fig. 


tcra)   and  Enibiid?e  being  transferred  doubtfully  to  Orthop- 
tera. 

Enderlein's  recent  and  tborough  studies  confirm  the  view 
that  Termitida%  Embiidaj,  Psocidie  and  Mallophaga  constitute 
a  single  order. 

5.  Plecoptera. — ^  Metamorphosis  direct.  Antennas  long, 
multiarticulate.  Mouth  parts  mandibulate.  Prothorax  large. 
Wings  two  pairs,  membranous,  coarsely  and  complexly  reticu- 
late; ec|ual  or  else  hind  wings  larger 
and  with  an  ample  plicate  anal  area. 
Abdomen  with  ten  segments  and  usu- 
ally a  pair  of  long  multiarticulate  cerci. 
Nymphs  thysanuriform,  aquatic;  adults 
unicjue  in  having  tracheal  gills.  Ex- 
ample, Ptcromircys  (Fig.  18).  A 
single  family,  Perlida;,  comprising  two 
hundred  si)ecies. 

6.  Ephemerida.  —  Metamorphosis 
direct.     Antennae    bristle-like.     Mouth 
parts    mandibulate,    but    atrophied    in 
the   adult.     Prothorax   small.      Wings 
membranous,  minutely  reticulate;  hind 
pair  much  the  smaller,  rarely  absent. 
Abdomen   slender,   with   ten   segments 
^nd    three    or    two    \'ery    long    multi- 
articulate cerci.       Integument   delicate.       Nymphs   thysanuri- 
form, aquatic.     Example,  Hcxagcnia  (Fig.  19).     Three  hun- 
dred species. 

7.  Odonata. — Metamorphosis  direct.  Antennae  inconspicu- 
ous, bristle-shaped.  Mouth  parts  mandibulate.  Prothorax 
small.  Wings  four,  elongate,  subequal,  similar,  membranous, 
minutely  reticulate,  with  a  costal  joint,  or  nodus.  Abdomen 
slender,  with  ten  segments.  Nymphs  thysanuriform,  aquatic. 
Example,  Lihcllula  (Fig.  20).  About  two  thousand  species 
have  been  described. 

8.  Thysanoptera    (Physopoda).  —  Metamorphosis  direct. 


A  chicken  louse,  Menopc 
Length,    2   mm. 


14 


ENTOMOLOGY 
Fig.  i8. 


Fig.  ly. 


Hexagenia  variabilis.     A,   nymph;    B,   imago.     Natural 


CLASSIFICATION 


15 


but  including  a  subpupa  stage.     Mouth  parts  suctorial.     Pro- 
thorax   long.     Tarsus   terminating   in   a   bladder-like   organ. 


Fig.  20. 


Libcllula   pulchcUa.     A,    last   nymphal    skin;    B,   imago.     Slightly   reduced. 


Wings  present,  rudimentary  or  absent,  the  two  pairs  narrow, 
equal,  similar,  with  few  or  no  veins  and  fringed  with  long 
hairs.     Abdomen  with  ten  segments.     Minute  insects.     Ex- 


Fig.  21 


ample,   Eutlirips    (Fig.   21).     About  one   hundred   and  fifty 
species  have  been  described. 


i6 


ENTOMOLOGY 


9.  Hemiptera.  —  Metamorphosis  direct  (excepting  male 
Coccidse).  Antennas  usually  few-jointed.  :Mouth  parts  suc- 
torial. Prothorax  usually  large.  Wings  usually  present, 
except  in  the  parasitic  forms.  Eighteen  thousand  species. 
Three  suborders  : 

Suborder  Heteroptera.— Wrings  four,  folded  flat;  front 
membranous   apically    (hemelytra), 

Fig.  22. 


Benaciis    griseus.      Slightly    reduced. 

overlapping  obliquely;  hind  wings  membranous.  Head  not 
deflexed.  Example,  Bcnacus  (Fig.  22).  About  twelve  thou- 
sand species. 

Suborder  Homoptera.— Wings  four,  sloping  roof-like,  sim- 
ilar and  meml^ranous  or  front  pair  somewhat  coriaceous 
throughout.  Head  deflexed.  Example,  Cicada  (Fig.  206). 
Six  thousand  species. 

Suborder  Parasita.  —  Wingless.  Eyes  simple  or  none. 
Thoracic  segments  intimately  united;  tarsus  with  a  single 
claw.  Integument  thin.  Parasites  upon  mammals.  Exam- 
ple, Pediculus  (Fig.  23).      Some  fifty  species  are  known. 

10.  Neuroptera. — Aletamorphosis  indirect.     Antenna^  con- 


CLASSIFICATION 


z;^. 


spicuous.        Mouth     parts     mandibulate.  Fig.  23. 

Prothorax  large.     Wings  almost  always 

foijr,  membranous,  subequal  or  else  hind 

pair    smaller,    complexly    reticulate,    not 

plicate.       Larvae     thy  sanuri  form     or     in 

some    cases    cruciform,    and    aquatic    or 

terrestrial.      Example,     Chrysopa     (Fig. 

24).     About    six    hundred    species    have 

been  named. 

II.  Mecoptera. — jNletamorphosis  indi- 
rect.    ]\Iouth  parts   mandibulate,   at   the 

end    of    a    deflexed    rostrum,    or    beak. 

Prothorax  small.     Wings  four,  elongate, 

membranous,   naked,   coarsely   reticulate, 

or   else   rudimentary   or   absent.     Larvre 

eruciform,  caterpillar-like,  with  numerous  prolegs,  carnivo- 
rous. Example,  Bitfacus  (Fig.  25).  A 
single  family,  Panorpid?e,  comprising  but 
few  known  species. 

12,  Trichoptera. — Metamorphosis  in- 
direct. Antennae  filiform.  Mouth  parts 
of  imago  rudimentary  or  imperfectly 
suctorial ;  mandibles  rudimentary  or 
absent.     Prothorax  small.     Wings  four, 

membranous,   hairy,  veins  moderate  in   number,   cross  veins 


Head  louse,  Pediculus 
capitis,  female.  Length, 
2    mm. 


Fig. 


Chrysopa  plorabiinda. 
Slightly   reduced. 


few;  hind  pair  almost  always 
the  larger,  with  plicate  anal 
area.  Larv?e  suberuciform, 
aquatic,  usually  case-forming. 
Example,  Molanna  (Fig.  26). 
Betw'een  five  and  six  hundred 
species  are  known. 

13.  Lepidoptera. — Metamor- 
phosis   indirect.     Mouth   parts 
suctorial,   mandibles  absent  or 
rudimentary   (except  in  a  few 
3 


Fig.  25. 


hftaciis    strigosu. 


Natural    size. 


i8 


ENTOMOLOGY 


generalized  species).  Prothorax  small.  Wings  four,  sim- 
ilar, membranous,  clothed  with  scales,  veins  moderate  in  num- 
ber, cross  veins  few.  Larvae  cruciform  (caterpillars),  phy- 
tophagous (almost  never  carnivorous),  mandibulate.  Some 
fifty  thousand  species  have  been  described.  Two  suborders, 
not  sharply  separated  from  each  other. 

Suborder  Heterocera. — Antenna?  of  various  forms,  but  not 
terminating   in   a    distinct   knob   or   club.     Frenulum   usually 


Fig.  26. 


Molanna  cinerea. 


diameters. — After   Felt. 


present.  Chiefly  nocturnal  in  habit.  Example,  Callosamia 
(Fig.  236). 

Suborder  Rhopalocera. — Antennae  simple,  terminatmg  m  a 
distinct  club  and  without  conspicuous  lateral  processes.  Fren- 
ulum absent.  Diurnal  normally.  Examples,  Papilio  (Fig. 
27),  Anosia  (Fig.  243,  A). 

14.  Coleoptera. — Metamorphosis  indirect.  Mouth  parts 
mandibulate.  Prothorax  large,  as  a  rule.  Wings  four ;  front 
pair  horny  (elytra),  meeting  in  a  straight  line;  hind  pair  mem- 
branous, often  folded.  Larvae  thysanuriform  or  eruciform. 
Example,  Hydrophilus  (Fig.  28).  About  fifteen  thousand 
species. 


CLASSIFICATION 


19 


15,  Diptera. — Metamorphosis  indirect.  Mouth  parts  typ- 
ically suctorial,  but  modified  for  piercing,  lapping-,  rasping-,  etc. 
Prothorax  small.  One  pair  of  wings  (mcsollioracic),  mem- 
branous. transi)arcnt.  with  few  \eins ;  wings  rudimentary  or 
absent,  however,  in  most  of  the  parasitic  species;  hind  wings 
represented  by  a  pair  of  knobbed  threads,  or  balancers.  Lar- 
vae cruciform,  with  the  head  frequently  reduced  to  a  mere 
vestige  with  or  without  a  pair  of  mandibles,  and  usually  with- 

FiG.  27. 


B 


Papilio   troilus.     A,  larva; 


larva   suspended   for   pupation;    C,   chrysalis. 
Natural   size. 


out  true  legs,  though  pseudopods  may  be  present.     Example, 
Tipiila   (Fig.  29).     About  forty  thousand  described  species. 

16.  Siphonaptera  ( Aphaniptera) . — Metamorphosis  indi- 
rect. Head  small.  Eyes  simple  or  absent.  Mouth  parts 
suctorial.  Body  laterally  compressed.  Thoracic  segments 
subequal.  Wings  absent  or  at  most  quite  rudimentary.  Lar- 
vae with  a  head,  mandibulate,  apodous.  Parasitic  insects. 
Example,  Ctcnoccphalns  (Fig.  30).  One  hundred  and  fifty 
species. 

17.  Hymenoptera. — Metamorphosis  indirect.  Mouth  parts 
at  the  same  time  mandibulate  and  suctorial.  Prothorax  usu- 
ally small.      Wings  four,  similar,  membranous,  transparent, 


ENTOMOLOGY 


with  a  few  irregular  veins  and  cells ;  hind  pair  the  smaller. 
Females  with  an  ovipositor,  modified  for  sawing,  boring  or 


Fig.  2^ 


Hydro[>hilus   triangularis.     Natural    size. 


Stinging.  Larvae  eruciform,  mandibulate,  caterpillar-like, 
with  head  and  legs,  or  else  maggot-like  and  apodous.  Twenty- 
five  or  thirty  thousand  species.     Two  suborders. 

Fig.  29. 


Tipula.     A,   larva;    B,   cast   pupal    skin;    C,    imago.      Slightly   reduced. 

Suborder  Terebrantia   (Phytophaga,   Sessiliventres) . — 

Abdomen  broadly  attached  to  the  thorax.     Ovipositor  modified 


CLASSIFICATION 


for  boring-,  sawing  or  cutting.  Larvns  with  complex  mouth 
parts  and  frequently  abdominal  legs.  Phytophag-ous.  Ex- 
ample, Trcnic.v  (h'ig.  31  ). 


Fig.  31.. 


Cat   and   dog   flea,    Ctciwccplialns   canis.     A,   larva    (after    Klinckel   d'Herculais)  ; 
B,   adult.      Length  of  adult,   2  nmi. 

Suborder  Aculeata  (Heterophaga,  Petiolata). — Abdomen 
petiolate  or  subpetiolate ;  first  abdominal  segment  transferred 
to  the  thorax.  Ovipositor 
often  modified  to  form  a 
sting.  Larvae  apodous.  Ex- 
ample. Apis  (Eig.  277). 

Interrelations  of  the 
Orders. — The  modern  clas- 
sification aims  to  express 
relationships,  and  these  are 
most  clearly  to  be  ascer- 
tained by  a  comparative 
study  of  the  facts  of  anat- 
omy and  development. 

The  most  generalized,  or 
primitive,  insects  are  the 
Thysanura.     Sul)tracting 

their  special,  or  adaptive,  peculiarities,  their  remaining  charac- 
ters may  properly  be  regarded  as  inheritances  from  some 
vanished  ancestral  type  of  arthropod.     This  primordial  type, 


Tremcx  columha.  A,  imago;  B,  larva 
(with  parasitic  larva  of  Tlialessa  attached). 
Natural   size. — After   Rilev. 


2  2  ENTOMOLOGY 

then,  probalily  liad  three  simple  and  equal  thoracic  segments 
differing  but  slightly  from  the  ten  abdominal  segments ;  three 
pairs  of  legs  and  no  wings;  three  pairs  of  exposed  biting 
mouth  parts;  a  pair  of  long  man3'-jointed  antennae  and  a  pair 
of  cerci  of  the  same  description ;  a  thin  naked  integument ;  a 
simple  straight  alimentary  canal  distinctly  divided  into  three 
primary  regions ;  a  ganglion  and  a  pair  of  spiracles  for  each 
of  the  three  thoracic  and  the  first  eight  abdominal  segments, 
if  not  all  the  latter;  no  metamorphosis;  functional  abdominal 
legs  and  active  terrestrial  habits. 

The  existing  form  that  best  meets  these  requirements  is 
Scolopendrella,  which  is  not  an  insect,  however,  but  belongs 
among  or  near  the  diplopods.  The  most  primitive  of  known 
insects  are  Anajapyx  and  Cauipodca,  through  which  other 
insects  trace  their  origin  to  the  stock  from  which  Symphyla 
and  Diplopoda  arose. 

Collembola,  though  specialized  in  several  important  ways, 
all  have  the  same  peculiar  kind  of  entognathous  mouth  parts 
as  Campodea  and  Japyx,  for  which  reason  and  many  others  it 
is  believed  that  Collembola  are  an  offshoot  from  the  thysanu- 
ran  stem.  Collembola,  however,  are  not  nearly  so  primitive 
as  Thysanura,  for  the  former  have  fewer  abdominal  segments 
than  the  latter,  exhibit  much  greater  concentration  of  the  ner- 
vous system,  and  are  uniquely  specialized  in  several  respects, 
notably  as  regards  the  ventral  tube  and  the  furcula,  or  spring- 
ing organ. 

Returning  to  Thysanura — the  genera  Machilis  and  Lcpisma 
show  decided  orthopteran  affinities ;  thus  their  eyes  are  com- 
pound and  their  mouth  parts  strongly  orthopteran ;  indeed,  the 
likeness  of  Lepisma  to  a  young  cockroach  is  striking,  as  is  also 
that  of  Japyx  to  a  young  forficulid. 

In  short,  as  Hyatt  and  Arms  express  it,  "  The  generalized 
form  of  Thysanura,  and  the  manner  in  which  it  reappears  in 
the  larvae  of  other  insects,  is  the  natural  key  of  the  classifi- 
cation." 

Orthoptera  probably  arose  directly  from  the  original  thys- 
anuriform  stem. 


CLASSIFICATION  23 

Platyptera,  as  a  whole,  are  most  nearly  related  to  Orthop- 
tera  on  the  one  hand  and  to  Plecoptera  on  the  other.  Termit- 
idse  have  strong  orthopteran  affinities  and  Embiidse  have  even 
been  placed  in  the  order  Orthoptera,  though  the  latter  family 
is  most  nearly  allied  to  Termitid.'c  and  Psocid?e.  These  two 
are  approached  rather  closely  by  Mallophaga  and  exhibit,  by 
the  way,  some  collembolan  characters,  as  Enderlein  has  lately 
pointed  out. 

Plecoptera,  which  Packard  placed  in  his  group  Platyptera, 
are  better  regarded  as  a  distinct  order  with  some  orthopteran 
and  many  ephemerid  and  odonate  affinities.  The  strong  re- 
semblance between  nymphs  of  Plecoptera,  Ephemerida  and 
Odonata  indicates  community  of  origin. 

Ephemerida  and  Odonata  are  well  circumscribed  orders, 
most  nearly  related  to  each  other,  but  sharply  separated,  nev- 
ertheless, by  differences  in  the  wings,  mouth  parts  and  other 
organs.  Ephemerida  are  almost  unique  among  insects  in  hav- 
ing a  pair  of  genital  openings — a  primitive  condition. 

Thysanoptera  form  a  distinct  order,  which  is  usually  placed 
next  to  Hemiptera,  chiefly  on  account  of  the  suctorial  mouth 
parts,  though  even  in  this  respect  there  is  no  close  agreement 
between  the  two  orders. 

Hemiptera  stand  alone  and  give  few  hints  of  their  ancestry. 
They  are  least  unlike  Orthoptera  and  possibly  originated  with 
Thysanoptera  from  some  mandibulate  and  winged  form.  The 
conversion  of  mandibulate  into  suctorial  organs  may  be  seen 
within  the  order  Collembola,  but  it  is  highly  improbable  that 
Hemiptera  arose  from  forms  like  Collembola.  Hemiptera  are 
exceptional  among  insects  with  a  direct  metamorphosis  in 
their  highly  developed  type  of  suctorial  mouth  parts. 

Metamorphosis  offers,  upon  the  whole,  the  broadest  criteria 
for  the  separation  of  insects  into  primary  groups.  All  the 
orders  considered  thus  far  are  characterized  either  by  no  meta- 
morphosis or  by  a  slight,  or  so-called  "  direct,"  or  "  incom- 
plete," transformation.  The  following  orders,  on  the  con- 
trary,  are   distinguished   by   an    "  indirect,"    or   "  complete," 


24  ENTOMOLOGY 

metamorphosis,  which  appears  in  Neuroptera  and  attains  its 
maximum  development  in  Diptera  and  Hymenoptera. 

With  Neuroptera  the  eruciform  type  of  larva  appears,  as  a 
derivative  of  the  earlier  thysanuriform  type.  The  larva  of 
Mantispo,  as  Packard  has  shown,  actually  passes,  during  its 
individual  development,  from  the  primary,  thysanuriform 
stage  to  the  secondary,  eruciform  condition. 

Mecoptera  form  an  isolated  order,  though  their  caterpillar- 
like larvae,  with  eleven  or  twelve  pairs  of  legs,  suggest  affini- 
ties with  Lepidoptera  and,  more  remotely,  with  the  tenthred- 
inid  Hymenoptera. 

Trichoptera,  while  much  like  Mecoptera  in  structure  and 
metamorphosis,  are  undoubtedly  closely  related  to  Lepidop- 
tera; in  view  of  the  extensive  and  deep-seated  resemblances 
between  caddis  flies  and  the  most  generalized  moths  (Microp- 
terygidae)  there  is  little  doubt  that  Trichoptera  and  Lepi- 
doptera originated  from  the  same  stock. 

The  origin  of  the  coherent  group  Coleoptera  is  by  no  means 
clear,  although  thysanuriform  larvae  occur  frequently  in  this 
order.  Packard  suggests  that  both  beetles  and  earwigs  arose 
from  some  thysanuroid  form  or  that  the  primitive  coleopterous 
larva  sprang  from  some  metabolous  neuropteroid  form.  In 
any  linear  arrangement  of  the  orders  the  position  of  Coleop- 
tera is  largely  arbitrary,  and  here  the  order  is  intruded  between 
Lepidoptera  and  Diptera  simply  for  want  of  a  more  satisfac- 
tory place. 

Lepidoptera,  Trichoptera  and  Mecoptera  are  probably 
branches  from  one  stem.  Lepidoptera,  Diptera  and  Hymen- 
optera are  reg'arded  by  Packard  as  having  had  a  common 
origin  from  metabolic  Neuroptera. 

Among  Diptera,  such  larvae  as  those  of  Culicidae  are  com- 
paratively primitive,  according  to  Packard,  and  larvae  of  Mus- 
cidae  are  secondary,  or  adaptive,  forms. 

Siphonaptera  used  to  be  regarded  as  Diptera  and  are  prob- 
ably an  offshoot  from  the  dipteran  stem. 

The  most  primitive  hymenopterous  larvae  are  those  of  the 


CLASSIFICATION 


25 


sawflies  (Tentliredinidie),  judging-  from  their  resemblance  to 
mecopterons  and  lepidopterous  larva?;  and  the  simple,  maggot- 
like form  of  the  larvae  of  ants,  bees,  wasps  and  parasitic 
Hymenoptera  is  due  to  secondary  modifications  in  correlation 
with  their  sedentary  mode  of  life. 

In  Diptera  and  Hymenoptera  the  phenomenon  of  metamor- 
phosis attains  its  greatest  complexity,  as  was  remarked. 
Opinions  differ  as  to  which  of  these  two  orders  is  the  more 
specialized.  Hymenoptera  are  commonly  called  the  "  high- 
est "  insects,  when  their  remarkable  psychological  development 
is  taken  into  account ;  but  from  a  purely  structural  standpoint 
it  is  hard  to  say  which  order  is  the  more  complex — indeed,  the 
two  orders  are  specialized  in  so  many  different  ways  that  no 
precise  comparison  can  be  made  between  them. 

The  following  diagram  (Fig.  32)  is  a  graphic  summary  of 
what  has  just  been  said  in  regard  to  the  genealogy  of  the 

Fig.  2,2. 


DIPTERA 


PLECOPTERA 
PLATYPTERA 

ORTHOPTERA 


HEMIPTERA 


COLEOPTERA 


THYSANURA 


Genealogical   diagram   of   the   orders  of  insects. 


orders  of  insects.     The  positions  of  Hemiptera  and  Coleoptera 
are  most  open  to  criticism.     The  central   group    (7")    is  the 


26  ENTOMOLOGY 

hypothetical  thysanuroid  source  of  ah  insects,  including  Thys- 
anura  themselves.  Though  Thysanura  and  Collembola  show 
no  traces  of  wings,  even  in  the  embryo,  it  should  be  borne  in 
mind  that  all  the  other  insects  probably  had  winged  ancestors 
and  that  it  is  more  reasonable  to  assume  a  single  winged  group 
as  a  starting  point  than  to  suppose  that  wings  originated  inde- 
pendently in  several  different  groups  of  insects. 


CHAPTER  II 
ANATOMY   AND   PHYSIOLOGY 

I.  Skeleton 

Number  and  Size  of  Insects. — The  imnil^er  of  insect  spe- 
cies already  known  is  about  300,000  and  it  is  safe  to  estimate 
the  total  number  of  existing  species  as  at  least  one  million. 

Among  the  largest  living  species  are  the  Venezuelan  beetle 
Dynastcs  Jicrculcs,  which  is  155  mm.  long,  and  the  Venezuelan 
grasshopper  Acrid ium  latrcillci,  which  has  a  length  of  166 
mm.  and  an  alar  expanse  of  240  mm.  Among  Lepidoptera, 
Attacus  atlas  of  Indo-China  spreads  240  mm.;  Attacus  ccesar 
of  the  Philippines,  255  mm. ;  and  the  Brazilian  noctuid  Erebus 
agrippina,  280  mm.  Some  of  the  exotic  wood-boring  larvae 
attain  a  length  of  150  mm. 

The  giants  among  insects  have  been  found  in  the  Carbonif- 
erous, from  which  Brong^niart  described  a  phasmid  (Titauo- 
pliasina)  as  being  one  fourth  of  a  meter  long. 

At  the  other  extreme  are  beetles  of  the  family  Trichoptery- 
gidse,  some  of  which  are  only  0.25  mm.  in  length,  as  are  also 
certain  hymenopterous  egg-parasites  of  the  families  Chalcid- 
ida2  and  Proctotrypidje. 

Thus,  as  regards  size,  insects  occupy  an  intermediate  place 
among  animals ;  though  some  insects  are  smaller  than  the 
largest  protozoans  and  others  are  larger  than  the  smallest 
vertebrates. 

Segmentation. — One  of  the  fundamental  characteristics  of 
arthropods  is  their  linear  segmentation.  The  subject  of  the 
origin  of  this  segmentation  is  far  from  simple,  as  it  involves 
some  of  the  most  difficult  cjuestions  of  heredity  and  variation. 
As  arthropod  segmentation  is  usually  regarded  as  an  inher- 
itance from  annelid-like  ancestors,  the  subject  resolves  itself 

27 


28  ENTOMOLOGY 

into  the  question  of  the  origin  of  the  segmented  from  the  nn- 
segmented  "  worms."  Cope,  Packard  and  others  give  the  me- 
chanical explanation  which  is  here  summarized.  In  a  thin- 
skinned,  unsegmented  worm,  the  flexures  of  the  body  initiated 
by  the  muscular  system  would  throw  the  integument  into 
folds,  much  as  in  the  leech,  and  with  the  thickening  of  the 
integument,  segmentation  would  appear  from  the  fact  that  the 
deposit  of  chitin  would  be  least  at  the  places  of  greatest  flex- 
ure, i.  e.,  the  valleys  of  the  folds,  and  greatest  at  the  places 
of  least  flexure,  i.  e.,  the  crests  of  the  folds.  This  explana- 
tion, which  has  been  elaborated  in  some  detail  by  the  Neo- 
Lamarckians,  applies  also  to  the  segmentation  of  the  limbs,  as 
well  as  the  body. 

Head. — In  an  insect  several  of  the  most  anterior  pairs  of 
primary  appendages  have  been  brought  together  to  co-operate 
as  mouth  parts  and  sense  organs,  and  ^the  segments  to  which 
they  belong  have  become  compacted  into  a  single  mass — the 
head — in  which  the  original  segmentation  is  difficult  to  trace. 
The  thickened  cuticula  of  the  head  forms  a  skull,  which 
serves  as  a  fulcrum  for  the  mouth  parts,  furnishes  a  base  of 
attachment  for  muscles  and  protects  the  brain  and  other 
organs. 

While  the  jaws  of  most  insects  can  only  open  and  shut, 
transversely,  their  range  of  action  is  enlarged  by  movements 
of  the  entire  head,  which  are  permitted  by  the  articulation 
between  the  head  and  thorax. 

As  a  rule,  one  segment  overlaps  the  one  next  behind ;  but 
the  head,  thougii  not  a  single  segment  of  course,  never  over- 
laps the  prothorax  in  the  typical  manner,  but  is  usually  re- 
ceived into  that  segment.  This  condition,  which  may  possibly 
have  been  brought  about  simply  by  the  backward  pull  of  the 
muscles  that  move  the  head,  has  certain  mechanical  advantages 
over  the  alternative  condition,  in  securing,  most  economically,, 
freedom  of  movement  of  the  head  and  protection  for  the  artic- 
ulation itself. 

The  size  and  strength  of  the  skull  are  usually  proportionate 


ANATOMY    AND    PHYSIOLOGY 


29 


to  the  size  and  power  of  the  moiitli  parts.  In  some  insects 
ahnost  the  entire  surface  of  the  head  is  occupied  by  the  eyes, 
as  in  Odonata  (Fig-.  20,  B)  and  Diptera  (Fio;.  39).  In  mus- 
cid  and  many  other  chpterous  larv.e,  or  "  mag-o-ots."  tlie  head 
is  reckiced  to  the  merest  rn(hment. 

Though  commonly  more  or  less  globose  or  ovate,  the  head 
presents  innumerable  forms ;  it  often  bears  unarticulated  out- 
growths of  various  kinds-,  some  of  which  are  plainly  adaptive, 
while  others  are  apparently  purposeless  and  often  fantastic. 

Sclerites  and  Regions  of  the  Skull. — The  dorsal  part  of 
the  skull  (Fig.  33)  consists  almost  entirely  of  the  cpicraiiiitiii, 


Fig.  32. 


mp 


Skull  of  a  grasshopper,  Melanoplus  diffcrcntialis.  a,  antenna;  c,  clypcus;  e,  com- 
pound eye;  /,  front;  g,  gena;  /,  labrum;  Ip,  labial  palpus;  m,  mandible;  Dtp,  maxillary 
palpus;   o,  ocelli;   oc,  occiput;   pg,   post-gena;   i',  vertex. 


which  bears  the  compound  eyes ;  it  is  usually  a  single  piece, 
or  sclcritc,  though  in  some  of  the  simpler  insects  it  is  divided 
by  a  Y-shaped  suture.  The  middle  of  the  face,  where  the 
median  ocellus  often  occurs,  is  termed  the  front;  ordinarily 
this  is  simply  a  region,  though  a  frontal  sclerite  exists  in 
some    insects.     Just  above  the  front,  and  forming  the  sum- 


30  ENTOMOLOGY 

mit  of  the  head,  is  the  region  known  as  the  vertex;  it 
often  bears  ocelh.  The  clypeus  is  easily  recognized  as  being 
the  sclerite  to  which  the  upper  Hp.  or  labium,  is  hinged, 
though  the  clypeus  is  not  invariably  delimited  as  a  distinct 
sclerite.  The  cheeks  of  an  insect  are  known  as  the  gcncc, 
and  post-gcncu  sometimes  occur.  On  the  under  side  of  the 
head  is  the  gula,  which  bears  the  under  lip,  or  labium.  That 
part  of  the  skull  nearest  the  prothorax  is  termed  the  occi- 
put; usually  it  is  not  delimited  from  the  epicranium,  though 
in  some  insects  it  is  continuous  with  the  post-gense  to 
form  a  distinct  sclerite.  The  occiput  surrounds  the  opening 
known  as  the  occipital  foramen,  through  which  the  oesophagus 

and  other  organs  pass  into 
"^4-  the  thorax.     The  membrane 

^V  ^^^<'''°        °^   ^^^^   "^^^   ^"   Orthoptera 

.'■''--?  W  '^^^  m-  X^         and  some  other  insects  con- 

'I       tains  small  cervical  sclerites, 

%      dorsal,  lateral  or  ventral  in 

|#f  J-       position;  these,  in  the  opin- 

^•* '-'  '         ion     of     Comstock,     pertain 

to  the  last  segment  of  the 
head.  Besides  those  de- 
scribed, a  few  other  cephalic 
sclerites    may    occur,    small 

Skull  of  a  grasshopper,  Dissosteira  caro-  and  iuCOnspicUOUS,  but  UCV- 
lina.  o.  occipital  foramen;  t,  t,  anterior  grthelCSS  of  Considerable 
arms  of  tentorium. 

morphological  importance. 
Tentorium. — In  the  head  is  a  chitinous  supporting  struc- 
ture known  as  the  tentorium.  This  consists  of  a  central  plate 
from  which  diverge  two  pairs  of  arms  extending  to  the  skull 
(Fig.  34).  The  central  plate  lies  between  the  brain  and  the 
suboesophageal  ganglion  and  under  the  oesophagus,  which 
passes  between  the  anterior  pair  of  arms.  The  tentorium 
braces  the  skull,  affords  muscular  attachments  and  holds  the 
cephalic  ganglia  and  the  oesophagus  in  place.  It  is  not  a  true 
internal  skeleton,  but  arises  from  the  same  ectodermal  laver 


/ 


ANATOMY    AND    PHYSIOLOGY 


31 


which  produces  the  external  cuticula;  though  authors  are  not 
agreed  as  to  the  details  of  the  development. 

Eyes. — The  eves  are  of  two  kinds — siiii/^lc  and  conipoiimL 
The  latter,  or  eves  proper,  conspicuous  on  each  side  of  the 
head,  are  of  common  occurrence 
except  in  the  larvae  of  most  holo- 
metaholous  insects,  in  some  gene- 
ralized forms  (as  Collemhola)  and 
in  parasitic  insects.  The  compound 
eyes  (Fig.  40)  are  convex  and  often 
hemispherical,  though  their  outline 
varies  greatly ;  thus  it  may  be  oval 
(Orthoptera)  or  triangular  (Noto- 
necfa),  while  in  the  aquatic  beetles 
of  the  family  Gyrinida;  (Fig.  35) 
each  eye  has  a  dorsal  and  a  ventral 
lobe,  enabling  the  insect  to  see  upward  and  downward  at  the 
same  time ;  so  also  in  Obcrca  and  other  terrestrial  beetles  of  the 
same  family.      Superficially,  a  compound  eye  is  divided  into 


Head  of  a  gyrinid  beetle,  Dincu- 
tus,   to    show   divided   eye. 


Fig.  36. 


Agglomerate  eyes  of  a  male 
coccid,  Leachia  fuscipennis. — 
After   SiGNORET. 


Fig.  37. 


\^  ^J^^-J 


c 


^ 

'M**^ 


Facets  of  a  compound 
eye  of  Melanoplns. 
Highly    magnified. 


erate  type  of  eye  (Fig.  36)  are  commonly  more  or  less  hex- 
agonal (Fig.  37),  as  the  result  of  mutual  pressure.  These 
facets  are  not  necessarily  equal  in  size,  for  in  dragon  flies  the 
dorsal  facets  are  frequently  larger  than  the  ventral.     In  diam- 


32 


ENTOMOLOGY 


eter  the  facets  range  from  .016  mm.  {Lycccna)  to  .094  mm. 
(Ceranibyx).  Their  number  is  often  enormous;  thus  the 
house  fly  (Mnsca  doincstica)  has  4,000  to  each  eye,  a  butter- 
fly (Papilio)   17,000,  a  beetle  {Mor- 


FiG.  38. 


dcUa)    25,000  and   a   sphingid   moth 


27,000 ;  on  the  other  hand,  ants  have 
from  400  down,  the  worker  ant  of 
Eciton  having  at  most  a  single  facet 
on  each  side  of  the  head. 

Ocelli.- — The  simple  eyes,  or  ocelli, 
appear  as  small  polished  lenses,  either 
lateral  or  dorsal  in  position.  Lateral 
ocelli  (Fig.  38)  occur  in  the  larvze  of 
most  holometabolous  insects  and  in 
parasitic  forms.  Dorsal  ocelli,  sup- 
plementary to  the  compound  eyes, 
occur  on  or  near  the  vertex,  and  are 
more  commonly  three  in  number,  ar- 
ranged in  a  triangle,  as  in  Odonata,  Diptera  (Fig.  39)  and 
Hymenoptera  (Fig.  40)  as  well  as  many  Orthoptera  and  He- 
miptera.     Few  beetles  have  ocelli  and  almost  no  butterflies 


Head      of      a 

caterp 

Samia      cecrofia, 

to       E 

lateral   ocelli. 

Fig.  39- 


Ocelli  and  compound  eyes  of  a  fly,  Phonnia  rcgina.     A,  male;  B,  female. 

(Lcreiiia  accius  with  its  one  ocellus  being  the  only  exception 
known),  though  not  a  few  moths  have  two  ocelli. 

As  explained  beyond,  the  compound  eyes  are  adapted  to  per- 
ceive form  and  movements  and  the  ocelli  to  form  images  of 


ANATOMY    AND    PHYSIOLOGY 


33 


objects  at  close  range  or  simply  to  distinguish  between  light 
and  darkness. 

Sexual  Differences  in  Eyes. — In  most  Diptera  (Fig.  39) 
and  in  Ilymenoptera  (Fig-.  40)  and  Ephemerida^  as  well,  the 
eyes  of  the  male  are  larger  and  closer  together  {lioloptic)  than 

1 10    [O 


Ocelli   and  compound   eyes   of   the   honey   bee,   Apis   mellifera.     A,   queen;    B,   drone. - 
After   Cheshire. 


those  of  the  female  (dichoptic) .  This  difference  is  attributed 
to  the  fact  that  the  male  is  more  active  than  the  female,  espe- 
cially in  the  matter  of  seeking  out  the  opposite  sex.  Among 
ants  of  the  same  species  the  different  forms  may  differ  greatly 
in  the  number  of  lateral  facets.  Thus  in  Formica  pratensis, 
according  to  Forel,  the  worker  has  about  600  facets  in  each 
eye,  the  queen  800-900  and  the  male  1,200. 

Blind  Insects. — Many  larva;,  surrounded  by  an  abundance 
of  food  and  living  often  in  darkness,  need  no  eyes  and  have 
none;  this  is  true  of  the  dipterous  "  maggots  "  and  many  other 
sedentary  larvae,  particularly  such  as  are  internal  parasites 
(Tachinidse,  Ichneumonidae),  or  such  as  feed  within  the  tis- 
sues of  plants  (many  Buprestidse,  Cerambycidae  and  Curculi- 
onid^e).  Subterranean  or  cavernicolous  insects  are  either  eye- 
less or  else  their  eyes  are  more  or  less  degenerate,  according 
to  the  amount  of  light  to  which  they  have  access.  The  state- 
ment is  made  that  blind  insects  never  have  functional  wings. 

Antennae. — The  antennae,  never  more  than  a  single  pair 
(though  embryonic  "  second  antennae  "  occur  in  Thysanura 
4 


34 


ENTOMOLOGY 


and  Collembola),  are  situated  near  the  compound  eyes  and 
frequently  between  them.  With  rare  exceptions  the  antennae 
have  always  several  and  usually  many  segments.  In  form 
these  organs  are  exceedingly  varied,  though  many  of  them 
may  be  referred  to  the  types  represented  in  Figs.  41-43. 


\^arious  forms  of  antennae.  A,  filiform,  Euschistus;  B,  setaceous,  Plathemis;  C, 
moniliform,  Catogenus;  D,  geniculate,  Bombiis;  f,  flagellum;  p,  pedicel;  s,  scape;  E, 
irregular,  Phormia;  a,  arista;  F,  setaceous,  Galerita;  G,  clavate,  Anosia;  H,  pectinate, 
male  Ptilodactyla;  I,  lamellate,  Lachnosterna;  J,  capitate,  Megalodacne ;  K,  irregular, 
Dineutus. 


Though  homologous  in  all  insects,  the  antennae  are  by  no 
means  equivalent  in  function.  They  are  commonly  tactile 
(grasshoppers,  etc.)  or  olfactory  (beetles,  moths)  and  occa- 
sionally auditory   (mosquito),  as  described  beyond,  but  may 


ANATOMY    AND    PHYSIOLOGY 


35 


he  adapted  for  other  than  sensory  functions.  Thus  the  anten- 
n;e  of  tlie  aquatic  heetle  Hydrophiliis  are  used  in  connection 
with     respiration     and     those 


to    hold 


Fig. 


IK   of   a   moth, 
male;   B, 


Snmia   cccropia. 
female. 


of    the    male    Mcloc 
the  female. 

Sexual  Differences  in  An- 
tennae.—  In  moths  of  the 
family  Saturniidas  {S.  cccro- 
pia, C.  promcthca,  etc.)  the 
pectinate  antennae  of  the  male 
are  larg-er  and  more  feathered 
than  those  of  the  female, 
and  (liiYer  also  in  having  more 
segments  (Fig.  42).  Here 
the  antennae  are  chieiiy  olfac- 
tory, and  the  reason  for  their 
greater  development  in  the 
male  appears  from  the  fact 
that  the  male  seeks  out  the  female  l)y  means  of  the  sense  of 
smell  and  depends  upon  his  antennas  to  perceive  the  odor  ema- 
nating from  the  opposite  sex. 

The  plumose  antennas  of  the  male  mosquito  (Fig.  43)  are 
highly  developed  organs  of  hearing,  and  are  used  to  locate  the 
female ;  they  have  delicate  fihrillae  of  various  lengths,  some  of 
which  are  thrown  into  sympathetic  vibration  by  the  note  of 
the  female  (p.  107). 

Mcloc  has  just  been  mentioned.  In  Sinmthunis  nialingrcnii 
(Collembola)  the  antennae  of  the  male  are  provided  with 
hooks  and  otherwise  adapted  to  grasp  those  of  the  female  at 
copulation. 

Though  systematists  have  recorded  many  instances  of  an- 
tennal  antigeny,  the  interpretation  of  these  sexual  differences 
has  received  very  little  attention ;  though  a  beginning  in  the 
subject  has  been  made  by  Schenk,  whose  results  will  be  re- 
ferred to  in  connection  with  the  sense  organs. 

Mouth  Parts. — On  account  of  their  great  range  of  diffe- 


36 


ENTOMOLOGY 


rentiation,  the  mouth  parts  are  of  fundamental  importance  to 
the  systematist,  particularly  for  the  separation  of  insects  into 
orders.  Most  of  the  orders  fall  into  two  groups  according 
as  the  mouth  parts  are  either  biting  {luandihulatc)  or  sucking 

Fig.  43- 


Antennae   of   mosquito,    Culcx  pipiens.     A,   male;    B,    female. 

(suctorial).  Collembola  and  Hymenoptera,  however,  com- 
bine both  functions ;  Diptera,  though  suctorial,  exhibit  various 
modifications  for  piercing,  lapping  or  rasping;  Thysanoptera 
are  partly  mandibulate  but  chiefly  suctorial ;  and  adult  Ephe- 
merida  and  Trichoptera  have  but  rudimentary  mouth  parts. 

The  mandibulate  orders  are  Thysanura,  Collembola  (pri- 
marily). Orthoptera,  Platyptera,  Plecoptera,  Ephemerida 
(rudimentarily  in  adult),  Odonata,  Neuroptera,  Mecoptera 
and  Coleoptera. 

The  mouth  parts  of  an  insect  consist  typically  of  lahniin, 
mandibles,  niaxillcc,  labium  and  hypo  pharynx  (Fig.  44), 
though  these  organs  differ  greatly  in  different  orders  of  in- 
sects. The  mandibulate,  or  primary  type,  from  which  the 
suctorial,  or  secondary  type,  has  been  deri\-ed,  will  be  consid- 
ered first. 

Mandibulate  Type. — The  iabruni,  or  upper  lip,  in  biting 


ANATOMY    AND    PHYSIOLOGY 


17 


insects  is  a  sini])lc  plate,  hing-ed  to  the  clypens  and  moving  up 
and  down,  though  capahle  of  protrusion  and  retraction  to  some 
extent.  It  coxers  tlie  nianthljles  in  front  .and  pulls  food  back 
to  these  organs.     On  the  roof  of  the  pharynx,  under  the  la- 

FiG.  44. 


Mouth  parts  of  a  cockroach,  Ischnoptera  pennsylranica.  A,  labrum;  B,  mandible; 
C,  hypopharynx;  D,  maxilla;  E,  labium;  c,  cardo;  g  (of  maxilla),  galea;  g  (of  labium), 
glossa;  /,  lacinia;  Ip,  labial  palpus;  m,  mentum;  mp,  maxillary  palpus;  p,  paraglossa; 
pf,  palpifer;  pg,  palpiger;  s,  stipes;  sm,  submentum.  B,  D  and  E  are  in  ventral 
aspect. 


l)rum  and  clypeus,  is  the  cpipharyii.v ;  this  consists  of  teeth, 
tubercles  or  bristles,  which  serve  in  some  insects  merely  to 
hold  food,  though  as  a  rule  the  epipharynx  in  mandibulate 
insects  bears  end-organs  of  taste  (Packard). 

The  mandibles,  or  jaws  proper,  move  in  a  transverse  plane, 
being  closed  by  a  pair  of  strong  adductor  muscles  and  opened 
by  a  pair  of  weaker  abductors.  The  mandible  is  almost 
always  a  single  solid  piece.  In  herbivorous  insects  (Fig. 
45,  y^)  it  is  compact,  bluntly  toothed,  and  often  bears  a  molar, 
or  crushing,  surface  behind  the  incisive  teeth.     In  carnivorous 


38 


ENTOMOLOGY 


Species  (B)  the  mandible  is  usually  long-,  slender  and  sharply 
toothed,  without  a  molar  surface.     Often,  as  in  soldier  ants. 


Various  furiiis  of  mandibles.     A,  Melanoplus;  B,  Cicindcla;  C,  Apis;  D,  Ontliophagns; 
E,    Chrysopa;   F-I,    soldier    termites    (after    Hagen). 

the  mandibles  are  used  as  piercing  weapons;  in  bees  (C)  they 
are  used  for  various  industrial  purposes ;  in  some  beetles  they 
are  large,  grotesque  in  form  and  appa- 
rently purposeless.  The  mandibles  of 
Ontliophagns  (D)  and  many  other  dung 
beetles  consist  chiefly  of  a  flexible  lam- 
ella, admirably  adapted  for  its  special 
purpose.  In  Euphoria  (Fig.  261 ),  which 
feeds  on  pollen  and  the  juices  of  fruits, 
the  mandibles,  and  the  other  mouth 
parts  as  well,  are  densely  clothed  with 
hairs.  In  the  larva  of  Chrysopa,  the 
inner  face  of  the  mandible  (Fig.  45,  £) 
has  a  longitudinal  groove  against  which 
the  maxilla  fits  to  form  a  canal,  through 
which  the  blood  of  plant  lice  is  sucked 
into  the  oesophagus.  In  termites  (F-I) 
the  mandibles  assume  curious  and  often 
inexplicable  forms. 

Next  in  order  are  the  inaxilkc,  or 
under  jaws,  which  are  less  powerful 
than  the  mandibles  and  more  complex,  consisting  as  they 
do    of    several    sclerites    (Figs.    44,    46).      Essentially,    the 


Maxilla  of  Harpalus 
caliginosus,  ventral  as- 
pect, c,  cardo;  g,  galea; 
I,  lacinia;  p,  palpus;  pf, 
palpi  fer;  s,  stipes;  sg, 
subgalea. 


ANATOMY    AND    PHYSIOLOGY 


39 


maxilla  consists  of  three  lobes,  namely,  palpus,  galea  and 
lacinia,  which  are  borne  by  a  stipes,  and  hinged  to  the  skull 
by  means  of  a  cardo.  The  palpus,  always  lateral  in  position, 
is  usually  four-  or  five-jointed  and  is  tactile,  olfactory  or  gus- 
tatory in  function.  The  lacinia  is  commonly  provided  with 
teeth  or  spines.  The  maxillae  supplement  the  mandibles  by 
holding  the  food  when  the  latter  open,  and  help  to  comminute 
the  food.  Additional  maxillary  sclerites.  of  minor  impor- 
tance, often  occur. 

The  labium,  or  under  lip,  may  properly  be  likened  to  a  united 
pair  of  maxillae,  for  both  are  formed  on  the  same  three-lobed 
plan.  This  correspondence  is  evident 
in  the  cockroach,  among  other  gener- 
alized insects.  Thus,  in  this  insect 
(Fig.  44)  : 


Fig.  47. 


Labium  = 

Maxill.e 

palpus  = 

palpus 

paraglossa  = 

galea 

ghssa  = 

lacinia 

palpigcr  = 

palpi  fa- 

mcntinn =^ 

sti  pi  tcs 

'bnu 

:  lit  Hill 

with   gula  = 

cai'dincs 

In  most  mandibulate  orders  the 
glossae  unite  to  form  a  single  median 
organ,  as  in  Harpalus  (Fig.  47,  g). 
The  labium  forms  the  floor  of  the 
pharynx  and  assists  in  carrying  food 
to  the  mandibles  and  maxillae. 

The    use    of    the    term    "  second 
maxillae  "    for   the  labium   of  an   in- 
sect is  open  to  objection,  as  it  implies  an  equivalence  with 
the   second    maxillae    of   Crustacea — which    is   by   no    means 
established. 

The  tongue,  or  hypo  pharynx,  is  a  median  fleshy  organ  (Fig. 
44)  which  is  usually  united  more  or  less  with  the  base  of  the 
labium.     In  insects  in  general,  the  salivary  glands  open  at  the 


Labium  of  Harpalus  caligi- 
nosiis,  ventral  aspect.  g, 
united  glossse,  termed  the 
glossa;  m,  mentum;  p,  palpus; 
pg,  palpiger;  pr,  paraglossa; 
sm,  submentum.  The  median 
portion  of  the  labium  beyond 
the  mentum  is  termed  the 
ligula^ 


40 


ENTOMOLOGY 


Fig.  48. 


Hypopharynx     of 
niimerus        talpoides. 
lingua;    s,    superlingu 
After   Hansen. 


base  of  the  hypopharynx.  In  the  most  generaHzed  insects, 
Thysanura  and  Collembola,  the  hypopharynx  is  a  compound 
organ,  consisting  of  a  median  ventral  lobe,  or  lingua,  and  two 
dorso-lateral  lobes,  termed  superlingiicu 
by  the  author.  Superlinguje  occur  in  a 
few  other  mandibulate  orders  (Orthop- 
tera,  Fig.  48;  Ephemerida,  Fig.  49),  but 
have  not  yet  been  recognized  in  the  more 
specialized  orders  of  insects. 

Suctorial  Types. — Owing  to  their 
greater  complexity,  suctorial  mouth  parts 
are  not  nearly  so  well  understood  as  the 
mandibulate  organs,  biit  enough  has  been 
learned  to  enable  us  to  homologize  the 
two  types,  even  though  morphologists  still  disagree  in  regard 
to  minor  details  of  interpretation. 

The  suctorial,  or  haustellate,  orders  are  Collembola  (in 
part),  Thysanoptera  (in  part),  Hemiptera,  Trichoptera  (im- 
perfectly) ,  Lepidoptera,  Dip- 
tera,  Siphonaptera  and  Hy- 
menoptera  (which  have 
functional^  mandibles,  how- 
ever). 

Hemiptera.  —  The  beak, 
or  rosiniui,  in  Hemiptera 
consists  (Fig.  50)  of  a 
conspicuous,  one-  to  four- 
jointed  labium,  which  en- 
sheathes  hair-like  mandibles  and  maxillse  and  is  covered 
above  at  its  base  by  a  short  labrum.  The  mandibles  and  max- 
illae are  sharply-pointed,  piercing  organs  and  the  former  fre- 
quently bear  retrorse  barbs  just  behind  the  tip;  the  two  max- 
illae lock  together  to  form  a  sucking  tube.  Though  primarily 
a  sheath,  the  labium  bears  at  its  extremity  sensory  hairs,  which 
are  doubtless  used  to  test  the  food.  This  general  description 
applies  to  all  Hemiptera  except  the  parasitic  forms,  which  pre- 


Hypopharynx  of  an 
gcnia.  I,  lingua;  si, 
After  Vayssiere. 

and 


ephemerid,    Hepta- 
sl,     superlinguae. — ■ 


ANATOMY    AND    PHYSIOLOGY 


41 


sent  special  modifications.     A  pharyngeal  pumping  apparatus 
is  present,  which  is  similar  in  its  general  plan  to  that  of  Lei)i- 
doptera  and  Diptera,  as  presently  described,  though  it  differs 
as  regards  the  smaller  details  of  construction. 
Fig.  50. 


Mouth  parts  of  a  liemipteron,  Bcnaciis  griseus.  A,  dorsal  aspect;  B,  transverse  sec- 
tion; C,  e.xtremity  of  mandible;  D,  transverse  section  of  mandibles  and  maxillx;  c, 
canal;   I,  labrum;   li,  labium;   m,  mandible;   m.v,  maxillae. 

Lepidoptera. — In  Lepidoptera,  excepting  Erioccpliala.  the 
labrum  is  reduced  (Fig.  51)  and  the  mandibles  are  either  rudi- 
mentary or  absent  (Rhopalocera).  The  two  maxillcC  are  rep- 
resented by  their  gale?e,  which  form  a  conspicuous  proboscis ; 
the  grooved  inner  faces  of  the  galeae  (or  lacinicC,  according  to 
Kellogg)  form  the  sucking  tube,  which  opens  into  the  cesoph- 
agus.  The  labium  is  reduced,  though  the  labial  palpi  (Fig. 
52)   are  well  developed.     The  so-called  rudimentary  mandi- 


to  be  lateral  projections  of  the  labrum  (Fig.  51)  and  he  terms 
them  pilifers. 


ENTOMOLOGY 


The  exceptional  structure  of  the  mouth  parts  in  the  gene- 
rahzed  genus  Eriocephala  {Micro pteryx)  sheds  much  Hght  on 

the  morphology  of  these 


Fig.  51. 


organs  in  other  Lepidop- 
tera.  as  Walter  and  Kel- 
logg ha\-e  shown.  In 
this  genus  there  are  func- 
tional mandibles ;  the 
maxilla  presents  palpus, 
galea,  lacinia,  stipes  and 
cardo,  though  there  is  no 
pr(  )b<3scis ;  the  labium  has 
well  developed  submen- 
tum,  mentum  and  palpi ;  a 
hypopharynx  is  present. 

The  sucking  apparatus, 
as  described  by  Burgess, 
Five  muscles,  originating 
Fig.  52. 


Head  of  a  sphingid  moth,  Phlegethontiiis 
sexta.  a,  antenna;  c,  clypeus;  e,  eye;  /,  labrum; 
m.    mandible;    p,    pilifer;   pr,   proboscis. 

is  essentially  like  that  of  Diptera. 
at  the  skull  and  inserted  on  the 
wall  of  a  pharyngeal  bulb,  serve 
to  dilate  the  bulb  that  it  may  suck 
in  fluids,  while  numerous  circular 
muscles  serve  by  contracting  suc- 
cessively to  squeeze  the  contents 
of  the  bulb  back  into  the  stomach  ; 
a  hypopharyngeal  valve  prevent? 
their  return  forward. 

Diptera.- — In  the  female  mos- 
quito the  mouth  parts  (Fig.  53) 
are  long  and  slender.  As  Dim- 
mock  has  found,  the  labrum  and 
epipharynx   combine^    to    form   a 


maxillae  are  delicate,  linear,  pierc- 
ing organs,  the  latter  being  barbed 
distally;  maxillary  palpi  are  pres- 
^  Kulagin,  however,  describes  them  as  remaining  separate. 


Head  of  a  butterfly,  J'anessa. 
labial  palpus;  p,  a,  antennae;  /, 
proboscis. 


ANATOMY    AND    PHYSIOLOGY 


43 


ent;  the  hypopharynx  is  linear  also  and  serves  to  conduct  sa- 
liva ;  the  labium  forms  a  sheath,  enclosing  the  other  mouth 
parts  when  they  are  not  in  use:  a  pair  of  sensory  lobes,  termed 
labella,  occur  at  the  extremity  o{  the  labium. 


Fig.  53. 


I  li       h  rj. 

.n  ^  mx 


Mouth  parts  of  female  mosquito,  Culcx  pipicns.  A,  dorsal  aspect;  B,  transverse 
section;  C,  extremity  of  maxilla;  D,  extremity  of  labrum-epipharynx;  a,  antenna;  e, 
compound  eye;  h,  hypopharynx;  /,  labrum-epipharynx;  li,  labium;  m,  mandible;  mx, 
maxilla;   p,   maxillary  palpus. — B,   after   Dimmock. 


The  oesophagus  is  dilated  to  form  a  bull),  or  sucking  organ, 
from  which  muscles  pass  outward  to  the  skull ;  when  these  con- 
tract, the  bulb  dilates  and  can  suck  in  fluids,  as  blood  or  water, 
which  are  forced  back  into  the  stomach  by  the  elasticity  of  the 
bulb  itself,  according  to  Dimmock ;  the  regurgitation  of  the 
food  is  prevented  by  a  valve. 

The  male  mosquito  rarely  if  ever  sucks  blood  and  its  mouth 
parts  differ  from  those  of  the  female  in  that  the  mandibles  are 


44 


ENTOMOLOGY 


aborted  and  the  maxilla;  slightly  developed,  but  with  long 
palpi,  while  the  hypophar^-nx  coalesces  with  the  labium,  and 
there  is  no  oesophageal  bulb. 

Hymenoptera. — In  the  honey  bee,  which  will  serve  as  a 
type,  the  labrum  (Fig.  54)  is  simple;  the  mandibles  are  well 
developed  instruments  for  cutting  and  other  purposes  and  the 

Fig.  54- 


Mouth  parts  of  the  honey  bee,  Apis  mclUfcra.  a,  base  of  antenna;  br,  brain;  c, 
clypeus;  h,  hypopharynx;  /,  labrum;  Ip,  labial  palpus;  m,  mentum;  mo,  mouth;  mx, 
maxilla;   sm,   submentum. — After   Cheshire. 

remaining  mouth  parts  form  a  highly  complex  suctorial  appa- 
ratus, as  follows.  The  tongue  is  a  long  flexible  organ,  ter- 
minating in  a  "  spoon  "  (Fig.  127)  and  clothed  with  hairs  of 
various  kinds,  for  gathering  nectar  or  for  sensory  or  mechan- 
ical purposes.  The  maxillre  and  labial  palpi  form  a  tube  em- 
bracing the  tongue,  while  the  epipharynx  fits  into  the  space 
between  the  bases  of  the  maxillre  to  complete  this  tube. 
Through  this  canal  nectar  is  driven,  by  the  expansion  and  con- 
traction of  the  tube  itself,  according  to  Cheshire,  except  that 
when  only  a  small  quantity  of  nectar  is  taken,  this  passes  from 
the  spoon  into  a  fine  "  central  duct,"  or  also  into  the  '*  side 
ducts,"  which  are  specially  fitted  to  convey  quantities  of  fluid 
too  small  for  the  main  tube.  For  a  detailed  account  of  the 
highly  complex  and  exquisitely  adapted  mouth  parts  of  the 
honey  bee,  the  reader  is  referred  to  Cheshire's  admirable  work 
or  to  Packard's  Text-Book. 

Segmentation  of  the   Head. — The  determination  of  the 


ANATOMY    AND    PHYSIOLOGY  45 

nuniljer  of  seo-ments  entering"  into  the  composition  of  the  insect 
head  has  heen  a  chfficiilt  problem.  As  no  sej^ment  l)cars  more 
than  one  pair  of  primary  aiiiiendao-es,  tlierc  are  at  least  as 
many  seg-ments  in  the  head  as  there  are  pairs  of  primary 
appendages.  On  this  basis,  then,  the  antenn;e,  mandibles, 
maxillae  and  labinm  may  be  taken  to  indicate  so  many  seg- 
ments; but  in  order  to  decide  whether  the  e)es.  labrnm  and 
hvpopharvnx  represent  segments,  other  than  ]nn"ely  anatom- 
ical evidence  is  necessary.  The  key  to  the  subject  is  furnished 
by  embryology.  At  an  early  stage  of  development  the  future 
segments  are  marked  off  by  transverse  grooves  on  the  ventral 
surface  of  the  embryo,  and  the  pairs  of  segmental  appendages 
are  all  alike  (Fig.  194),  or  equivalent,  though  later  they  dif- 
ferentiate into  antenn;c,  mouth  parts,  legs,  etc.  Moreover,  the 
nervous  system  exhibits  a  segmentation  which  corresponds  to 
that  of  the  entire  insect;  in  other  words,  each  pair  of  primitive 
ganglia,  constituting  a  neuromcrc,  indicates  a  segment.  Now 
in  front  of  the  oesophagus  three  primitive  segments  appear,  each 
with  its  neuromere  (Fig.  55)  :  first  in  position,  an  ocular  seg- 
ment, destined  to  bear  the  compound  eyes;  second,  an  antennal 
segment;  third,  an  intercalary  (prciiiaiulibitlar)  segment, 
wdiich  in  the  generalized  orders  Thysanura  and  Collembola 
bears  a  transient  pair  of  appendages  that  are  probably  homol- 
ogous with  the  second  antennae  of  Crustacea.  In  the  adult, 
the  ganglia  of  these  three  segments  have  united  to  form  the 
brain,  and  the  original  simplicity  and  distinctness  have  been 
lost.  The  labrum,  by  the  way,  does  not  represent  a  pair  of 
appendages,  but  arises  as  a  single  median  lobe.  Behind  the 
oesophagus,  three  embryonic  segments  are  clearly  distinguish- 
able, each  with  its  pair  of  appendages,  namely,  ;/;an(//6H/tfr, //m.i-- 
illary  and  labial.  Finally,  the  hypopharynx,  or  rather  a  part  of 
it,  claims  a  place  in  the  series  of  segmental  appendages,  as  the 
author  has  maintained ;  for  in  Collembola  its  two  dorsal  con- 
stituents, or  supcrlingucr,  develop  essentially  as  do  the  other 
paired  appendages  and,  moreover,  a  superlingual  neuromere 
(Fig.    55)    exists.     The   four  primitive  ganglia   immediately 


46 


ENTOMOLOGY 


behind  the  mouth  eventually  combine  to  form  the  suboesopha 
geal  ganglion. 

To  summarize — the  head  of  an  insect  is  composed  of  at  least 
six  segments,  namely,  ocular,  antennal,  intercalary,  mandibu- 
lar, maxillary  and  labial ;  and  at  most  seven,  since  a  superlin- 
gual  segment  occurs  between  the  mandibular  and  maxillary 
segments  in  Collembola  and  probably  Thysanura,  though  it 
has  not  yet  been  discovered  in  the  more  specialized  insects. 


Fig.  5 


Paramedian  section  of  an  embryo  of  the  collembolan  Aniirida  maritima,  to  show 
the  primitive  cephalic  ganglia.  /,  ocular  neuromere;  2,  antennal;  s,  intercalary;  4, 
mandibular;  5,  superlingual;  6,  maxillary;  7,  labial;  i',  protboracic;  9,  mesotboracic; 
a,  antenna;  /,  labrum;  li,  labium;  P,  P,  l^,  thoracic  legs;  m,  mandible;  m.v,  maxilla. 
*— After  FoLSOM. 


Thorax. — The  thorax,  or  middle  region,  comprises  the 
three  segments  next  behind  the  head,  which  are  termed,  respec- 
tively, pro-,  mcso-  and  inetathorax.  In  aculeate  Hymenop- 
tera,  however,  the  thoracic  mass  includes  also  the  first  abdom- 
inal segment,  then  known  as  the  propodeuin,  or  median  seg- 
ment.    Each  of  the  three  thoracic  segments  bears  a  pair  of 


ANATOMY    AND    PHYSIOLOGY 


47 


ps 


Diagram  of  the  principal  scle- 
rites  of  a  thoracic  segment,  em, 
epimeron;  es,  episternum;  p, 
praescutum;  pr,  parapteron;  ps, 
postscutellum;  s,  scutum;  si, 
scutellum;     st,     sternum. — After 

COMSTOCK. 


legs  in  almost  all  adnlt  insects,  but  only  the  meso-  and  meta- 
thorax  may  bear  wings. 

The  differentiation  of  the  thorax  as  a  distinct  region  is  an 
incidental  result  of  the  development  of  the  organs  of  locomo- 
tion, particularly  the  wings.     Thus 
in     legless     (apodoiis)     larvcC     the  ""-.S'- 

thoracic  and  abdominal  segments 
are  alike ;  when  legs  are  present,  but 
no  wings,  the  thoracic  segments  are 
somewhat  enlarged ;  and  when 
wings  occur,  the  size  of  a  wing- 
bearing  segment  depends  on  the  vol- 
ume of  the  wing  muscles,  wdiich  in 
turn  is  proportionate  to  the  size  of 
the  wings.  When  \yings  are  absent 
(as  in  Thysanura  and  Collembola) 
or  the  two  pairs  equal  in  area  (as 
in  Termitidse,  Odonata,  Trichoptera 
and  most  Lepidoptera)  the  meso-  and  metathorax  are  equal.  If 
the  fore  wdngs  exceed  the  hind  ones  (Ephemeridce,  Hymenop- 
tera)  the  mesothorax  is  proportionately  larger  than  the  meta- 
thorax ;  as  also  in  Diptera,  where  no  hind  wings  occur.  If 
the  fore  wings  are  small  (Coleoptera)  or  almost  absent  (Sty- 
lopidse)  the  mesothorax  is  correspondingly  smaller  than  the 
metathorax.  The  prothorax,  which  never  bears  wings,  may 
be  enlarged  dorsally  to  form  a  protective  shield,  as  in  Orthop- 
tera,  Hemiptera  and  Coleoptera;  or,  on  the  contrary,  may  be 
greatly  reduced,  as  in  Ephemerida.  Odonata,  Lepidoptera  and 
Hymenoptera.  In  the  primitive  Apterygota  the  prothorax 
may  become  reduced  (many  Collembola)  or  slightly  enlarged 
(Lepisnia) . 

The  dorsal  wall  of  a  thoracic  segment  is  termed  the  notuui, 
or  tergum;  the  ventral  wall,  the  sternum;  and  each  lateral  wall, 
a  pleuron;  the  restriction  of  these  terms  to  particular  segments 
of  the  thorax  being  indicated  by  the  prefixes  pro-,  meso-  or 
Dicta-.     These  parts  are  usually  divided  by  sutures  into  dis- 


48 


ENTOMOLOGY 


Fig.  57, 


tinct  pieces,  or  sclerites,  as  represented  diagrammatically  in 
Fig.  56.     Thus  the  tergnm  of  a  wing-bearing  segment  is  re- 
garded as  being  composed  of  four  sclerites  (tcrgitcs,  Fig.  57), 
namely  and  in  order,  prccscutuiii,  sciitum,  scutcUnm  and  post- 
scutcUimi.     The  scutum  and  scutellum  are  commonly  evident, 
but    the   two   other   sclerites    are 
usually  small  and  may  be  absent. 
Each  pleuron  consists  chiefly  of 
two  sclerites  {plciwitcs,  Fig:  58), 
separated   from   each  other  by  a 
more     or     less     oblique     suture. 
The  anterior  of  these  two,  which 
joins  the  sternum,  is  termed  the 
cpistcniuni;    the    other,    the    cpi- 
mcron.     The    former    is    divided 
into  two  sclerites  in  Odonata  and 
both  are  so  divided  in  Neuroptera. 
The    sternum,    though    usually 
a    single    plate,    is    in    some    in- 
stances   divided    into    halves,    as 
in    the    cockroach,    or    even    into 
five  sclerites   (Forficulidse). 
To  these  should  be  added  the 
pair 
of    erectile    appendages    of    the 
prothorax;  and  the  paraptera,  or  fcgulcu,  of  Lepidoptera  and 
Flymenoptera — a  pair  of  small  sclerites  at  the  bases  of  the 
front  wings. 

Each  thoracic  segment  bears  a  pair  of  spiracles  in  the  em- 
bryo and  in  some  adults  as  well  {Campodca,  Heteroptera), 
but  in  most  imagines  there  are  only  two  pairs  of  thoracic 
spiracles,  the  suppressed  pair  being  usually  the  prothoracic. 

The  sclerites  of  the  thorax  owe  their  origin  probably  to 
local  strains  on  the  integument,  brought  about  by  the  muscles 
of  the  thorax.  Thus  the  primitively  wingless  Thysanura  and 
Collembola   have   no   hard   thoracic   sclerites,   though   certain 


Dorsal  aspect  of  the  thorax  of  a 
beetle,  Hydrous  piceus.  I,  pronotum; 
2,  mesoprjescutum;  j,  mesoscutum;  4, 
niesoscutellum;  5,  mesopostscutellum; 
6,    metaprKscut,um;    7,    metascutum;    5, 

metascutellum;    9,    metapostscutellum.     p^f^j^j^     ^f     Lcpidoptcra a 

—After  Newport.  t         ^  i  i 


ANATOMY    AND    PHYSIOLOGY 


49 


creases  about  the  Ijases  of  the  legs  may  be  reg-arded  as  incipi- 
ent sutures,  produced  mechanically  by  the  movements  of  the 


'"13 


Ventral  aspect  of  a  carabid  beetle,  Galerita  Janus,  i,  prosternum;  2,  proepisternum, 
3,  proepimeron;  4,  coxal  cavity;  5,  inflexed  side  of  pronotum;  6,  mesosternum;  7,  meso- 
episternum;  8,  mesoepimeron;  9,  metasternum;  10,  antecoxal  piece;  11,  metaepisternum; 
12,  metaepimeron;  13,  inflexed  side  of  elytron;  a,  sternum  of  an  abdominal  segment; 
an,  antenna;  c,  coxa;  f,  femur;  Ip,  labial  palpus;  md,  mandible;  mp,  maxillary  palpus; 
t,  trochanter;   tb,  tibia;   ts,  tarsus. 


legs.     In  soft  nymphs  and  larvae,  the  sclerites  do  not  form  until 
the  wings  develop ;  and  in  forms  that  have  nearly  or  quite  lost 
their  wings,  as  Pediculidse,  Mallophaga,Siphonaptera  and  some 
5 


so 


ENTOMOLOGY 


Fig.  59. 


parasitic  Diptera,  the  sclerites  of  the  thorax  tend  to  disappear. 
Furthermore,  the  absence  of  sclerites  in  the  prothorax  is  prob- 
ably due  to  the  lack  of  prothoracic  wings,  notwithstanding-  the 
so-called  obsolete  sutures  of  the  pronotum  in  grasshoppers. 

Endoskeleton. — An  insect  has  no  internal  skeleton,  strictly 
speaking,  though  the  term  endoskeleton  is  used  in  reference  to 
certain  ingrowths  of  the  external  cuticula  which  serve  as  me- 
chanical supports  or  as  protections 
for  some  of  the  internal  organs. 
The  tentorium  of  the  head  has  al- 
ready been  referred  to.  In  the 
thorax  three  kinds  of  chitinous  in- 
growths may  be  distinguished  ac- 
cording to  their  positions  :  ( i )  phrog- 
inas,  or  dorsal  projections;  (2) 
apodeines,  lateral;  (3)  apophyses, 
ventral.  The  phragmas  (Fig.  59) 
are  commonly  three  large  plates, 
pertaining  to  the  meso-  and  meta- 
thorax,  and  serving  for  the  origin 
of  indirect  muscles  of  flight  in 
Lepidoptera,  Diptera,  Hymenoptera 
and  other  strong-winged  orders.  The 
apodemes  are  comparatively  small  in- 
growths, occurring  sometimes  in  all 
three  thoracic  segments,  though  usu- 
ally absent  in  the  prothorax.  The 
apophyses  occur  in  each  thoracic  seg- 
ment as  a  pair  of  conspicuous  proc- 
esses, which  either  remain  separate 
or  else  unite  more  or  less ;  leaving,  however,  a  passage  for  the 
ventral  nerve  cord. 

These  endoskeletal  processes  serve  chiefly  for  the  origin  of 
muscles  concerned  with  the  wings  or  legs,  and  are  absent  in 
such  wingless  forms  as  Thysanura,  Pediculidze  and  Mal- 
lophaga. 


Transverse  sections  of  the 
thoracic  segments  of  a  beetle, 
GoUathus,  to  show  the  endo- 
skeletal processes.  A,  pro- 
thorax; B,  mesothorax;  C, 
metathorax;  a,  a,  apophyses; 
ad,  apodeme;  p,  phragma. — 
After  KoLBE. 


ANATOMY    AND    PHYSIOLOGY 


51 


Vir,.   60. 


tb 


Some  ambiguity  attends  the  use  of  these  terms.  Thus  some 
writers  use  the  term  apodemes  for  apophyses  and  others  apply 
the  term  apodeme  to  any  of  the  three 
kinds  of  ingrowths. 

Legs. — Tn  ahnost  all  adult  insects  and 
in  most  larv;c  each  of  the  three  thoracic 
segments  bears  a  pair  of  legs.  The  leg 
is  articulated  to  the  sternum,  episternum 
and  epimercMi  and  consists  of  five  seg- 
ments (Fig.  60).  in  the  following  order: 
coxa,  f  roc  Jia  liter,  femur,  tibia,  tarsus. 
The  coxa,  or  basal  segment,  often  has  a 
posterior  sclerite.  the  trochantinc}  The 
trochanter  is  small,  and  in  parasitic 
Hymenoptera  consists  of  two  subseg- 
ments.  The  femur  is  usually  stout  and 
conspicuous,  the  tibia  commonly  slender. 
The  tarsus,  rarely  single-jointed,  consists 
usually  of  five  segments,  the  last  of  which 
bears  a  pair  of  claws  in  the  adults  of 
most  orders  of  insects,  and  a  single  claw 
in  larv£e ;  between  the  claws  in  most 
imagines  is  a  pad.  usually  termed  the 
pulvillus,  or  cnipodiuin. 

Adaptations  of  Legs. — The  legs  ex- 
hibit a  great  variety  of  adaptive  modifica- 
tions. A  walking  or  running  insect,  as  a 
carabid  or  cicindelid  beetle  (Fig.  62.  A)  presents  an  average 
condition,  as  regards  the  legs.  In  leaping  insects  (grasshop- 
pers, crickets.  Halfica)  the  hind  femora  are  enlarged  (B)  to 
accommodate  the  powerful  extensor  muscles.  In  insects  that 
make  little  use  of  their  legs,  as  May  flies  and  Tipulidas,  these 
appendages  are  but  weakly  developed.     The  spinous  legs  of 

^  But  on  account  of  the  ambiguous  use  of  this  last  term,  the  name  mcron 
(Fig.  61),  proposed  by  WaUon,  is  to  be  preferred. 


Leg  of  a  beetle,  Calo- 
soma  calidum.  c,  coxa; 
cl,  claws;  f,  femur;  s, 
spur;  t^-t^,  tarsal  seg- 
ments; tb,  tibia;  tr, 
trochanter. 


52 


ENTOMOLOGY 


Fig.  6i. 


Left  hind  leg  of  Bittacus.  c,  coxa 
genuina;  em,  epimeron;  es,  episternum;  /, 
femur;    m,   meron;    t,   trochanter. 


dragon  flies  form  a  basket  for  catching  the  prey  on  the  wing. 
Modifications  of  the  front  legs  for  the  purpose  of  grasping 
occur  in  many  insects,  as  the  terrestrial  families  Mantidse  (C) 
and    Reduviid?e   and    the   aquatic    families    Belostomid^e    and 

Naucoridae  {D).  Swim- 
ming species  present  special 
adaptations  of  the  legs  (Fig. 
228),  as  described  in  the 
chapter  on  aquatic  insects. 
In  digging  insects,  the  fore 
legs  are  expanded  to  form 
shovel-like  organs,  notably 
in  the  mole-cricket  (Fig.  62, 
E) ,  in  which  the  fore  tibia 
has  some  resemblance  to  the 
human  hand,  while  the  tarsus  and  tibia  are  remarkably  adapted 
for  cutting  roots,  after  the  manner  of  shears.  The  Scara- 
bseidas  have  fossorial  legs,  the  anterior  tarsi  of  which  are  in 
some  genera  reduced  (F)  or  absent;  they  are  rudimentary  in 
the  female  {G)  of  Phancuus  carnifex  and  absent  in  the  male 
(//),  and  absent  in  both  sexes  of  Deltochilum.  Though 
females  of  Phancuus  lose  their  front  tarsi  by  digging,  the  de- 
generate condition  of  these  organs  cannot  be  attributed  to  the 
inheritance  of  a  mutilation,  but  may  have  been  brought  about 
by  disuse ;  though  no  one  has  explained  why  the  two  sexes 
should  differ  in  this  respect.  Many  insects  use  the  legs  to 
clean  the  antennae,  head,  mouth  parts,  wings  or  legs ;  the  honey 
bee  (with  other  bees,  also  ants,  Carabidse,  etc.)  has  a  special 
antenna-cleaner  on  the  front  legs  (Fig.  263,  D),  which  is 
described,  with  other  interesting  modifications  of  the  legs,  on 
page  271. 

Indeed,  the  legs  serve  many  such  minor  purposes  in  addi- 
tion to  locomotion.  They  are  generally  used  to  hold  the 
female  during  coition,  and  in  several  genera  of  Dytiscid?e 
(Dytiscus,  Cybister)  the  male  (Fig.  62,  /)  has  tarsal  disks  and 
cupules,  chiefly  on  the  front  tarsi,  for  this  purpose.     Among 


ANATOMY    AND    PHYSIOLOGY 


53 


Fig.  62. 


Adaptive  modifications  of  the  legs.  A,  Cicindela  se.vguttata;  B,  Nemohius  vittatus, 
hind  leg;  C,  Stagmomantis  Carolina,  left  fore  leg;  D,  Pelocoris  femorata,  right  fore 
leg;  E,  Gryllotalpa  borealis,  left  fore  leg;  F,  Canthon  lavis,  right  fore  leg;  G,  PJiancciis 
carnifex,  fore  tibia  and  tarsus  of  female;  H,  P.  carnifex,  fore  tibia  of  male;  /,  Dytis- 
cus  fascizentris,  right  fore  leg  of  male;  c,  coxa;  /,  femur;  s,  spur;  t,  trochanter;  tb, 
tibia;   ts,  tarsus. 


54 


ENTOMOLOGY 


Fig.  63. 


Other  secondary  sexual  peculiarities  of  the  legs  may  be  men- 
tioned the  tibial  brushes  of  the  male  Catocala  concnmhens, 
regarded  as  scent  organs,  and  the  queer  appendages  of  male 
Dolichopodidse  that  dangle  in  the 
air  as  these  flies  perform  their 
dances. 

The  pulvillus  is  commonly  an 
adhesive  organ.  In  flies  it  has 
glandular  hairs  that  enable  the  in- 
sects to  walk  on  smooth  surfaces 
and  to  walk  upside  down ;  so  also 
in  many  beetles  and  notably  in  the 
honey  bee  (Fig.  63)  ;  in  this  insect 
the  pulvillus  is  released  rapidly 
from  the  surface  to  which  it  has 
been  applied,  by  rolling  up  from  the 
edges  inward. 

Sense  organs  occur  on  the  legs. 
Thus  tactile  hairs  are  almost  always 
present  on  these  appendages,  while 
auditory  organs  occur  on  the  front  tibise  of  Locustidae,  Gryllidie 
and  some  ants.    Finally,  the  legs  may  be  used  to  produce  sound, 

Fig.  64. 


Foot  of  honey  bee,  Apis  mcl- 
lifcra.  c.  c,  claws;  p,  pulvillus; 
fi-f",  tarsal  segments. — After 
Cheshire. 


Caterpillar   of  Plilegethontius  sexta.     Natural   size. 


ANATOMY    AND    PHYSIOLOGY 


55 


as  in  Stenohothrus  and  such  other  AcridiicLx  as  stridulate  by 
rubbing  the  femora  against  the  tegmina. 

Legs  of  Larvae. — Tlioracic  legs,  terminating  in  a  single 
claw,  are  present  in  most  larvce.  Cateri)illars  have,  in  addi- 
tion, fleshy  abdominal  legs  (Fig.  64)  ending  in  a  circlet  of 
hooks.  Most  caterpillars  have  five  pairs  of  these  legs  (on 
abdominal  segments  3,  4,  5,  6  and  10),  but  the  rest  vary  in 
this  respect.  '  Thus  Lagoa  has  seven  pairs  (segments  2-7  and 
10)  and  GeometridcT  two  (segments  6  and  10),  while  a  few 
caterpillars    (Tischcria,   Limacodcs)    have    none.     Larvae    of 

Fig.  65. 


Mechanics  of  an  insect's  leg.  a,  axis  of  coxa;  c,  coxa;  cl,  claw;  e,  extensor  of 
tibia;  ec,  extensor  of  claw;  et,  extensor  of  tarsus;  f,  flexor  of  tibia;  fc,  flexor  of 
claw;  ft,  flexor  of  tarsus;  r,  r,  rotators  of  coxa;  s,  spur;  t,  trochanter  muscle  (elevator 
of  femur)  ;   ti,  tibia. — After  Graber. 

saW'  flies  (Tenthredinidas)  have  seven  or  eight  pairs  of  abdom- 
inal legs  and  larv?e  of  most  Panorpidse,  eight  pairs.  Not  a 
few  coleopterous  larv?e  (some  Cerambycidre,  Phytonomiis) 
also  have  abdominal  legs,  which  are  incompletely  developed, 
however,  as  compared  with  those  of  Lepidoptera. 

The  legless,  or  apodous,  condition  occurs  frequently  among 
larvae  and  always  in  correlation  wath  a  sedentary  mode  of  life; 
as  in  the  larvae  of  many  Cerambycidse,  nearly  all  Rhynchoph- 
ora,  a  few^  Lepidoptera,  all  Diptera,  and  all  Hymenoptera  ex- 
cept Tenthredinida?,  Siricidre,  and  other  Terebrantia. 


56 


ENTOMOLOGY 


Fig.  66. 


Among  adult  insects,  female  scale  insects  are  exceptional  in 
being  legless. 

Walking. — An  adult  insect,  when  walking,  normally  uses 
its  legs  in  two  sets  of  three  each ;  thus  the  front  and  hind  legs 
of  one  side  and  the  middle  leg  of  the  other  move  forward 
almost  simultaneously — though  not  quite,  for  the  front  leg 
moves  a  little  before  the  middle  one, 
which,  in  turn,  precedes  the  hind  leg. 
During  these  movements  the  body  is  sup- 
ported by  the  other  three  legs,  as  on  a 
tripod.  The  front  leg,  having  been  ex- 
tended and  its  claws  fixed,  pulls  the  body 
forward  by  means  of  the  contraction  of 
the  tibial  flexors;,  the  hind  leg,  on  the 
contrary,  pushes  the  body,  by  the  short- 
ening of  the  tibial  extensors,  against  the 
resistance  afforded  by  the  tibial  spurs ;  the 
middle  leg  acts  much  like  the  hind  one, 
but  helps  mainly  to  steady  the  body. 
Different  species  show  different  peculiari- 
ties of  gait.  In  its  analysis,  the  walking 
of  an  insect  is  rather  intricate,  as  Graber 
and  Marey  have  shown. 

The  mode  of  action  of  the  principal 
leg  muscles  may  be  gathered  from  Fig. 
65.  Here  the  flexion  of  the  tibia  would 
cause  the  tibial  spur  (s)  to  describe  the 
line  si;  and  the  backward  movement  of 
die  leg  due  to  the  upper  coxal  rotator  r 
would  cause  the  spur  to  follow  the  arc  s  j. 
As  the  resultant  of  both  these  movements, 
the  path  actually  described  by  the  tibial 
spur  is  s  2 :  then,  as  the  leg  moves  forward,  the  curve  is  con- 
tinued into  a  loop. 

Caterpillars  use  their  legs  successively  in  pairs,  and  when 
the  pairs  of  legs  are  few  and  widely  separated,  as  in  Geomet- 
ridae,  a  curious  looping  gait  results. 


Muscles  of  left  mid 
leg  of  a  cockroach,  pos- 
terior aspect.  ahc, 
ductor  of  coxa; 
adductor  of  coxa ; 
extensor  of  femur; 
extensor  of  tibia; 
flexor  of  femur; 
flexor  of  tibia ; 
flexor  of  tarsus;  rt 
tractor  of  tarsus. — After 
MiALL  and   Denny. 


ANATOMY    AND    PHYSIOLOGY  57 

The  leg-  muscles  of  a  cockroach  are  shown  in  ¥\s^.  66. 

Leaping. — The  hind  legs,  inserted  nearest  the  center  of 
gravity,  are  the  ones  employed  in  leaping,  and  they  act  to- 
gether. A  grasshopper  prepares  to  jnmp  hy  hending  the 
femur  back  against  the  tibia;  to  make  the  jump,  the  tibia  is 
jerked  back  against  the  ground,  into  which  the  tibial  spurs  are 
driven,  and  the  straightening  of  the  leg  by  means  of  the  pow- 
erful extensors  throws  the  insect  into  the  air.  At  the  distal 
end  of  the  femur  are  two  lobes,  one  on  each  side  of  the  tibia, 
which  prevent  woljbling  movements  of  the  tibia. 

Wings. — The  success  of  insects  as  a  class  is  to  be  attributed 
largely  to  their  possession  of  wings.  These  and  the  mouth 
parts,  surpassing  all  the  other  organs  as  regards  range  of  dif- 
ferentiation, have  furnished  the  best  criteria  for  the  purposes 
of  classification.  The  wings  of  insects  present  such  countless 
differences  that  an  expert  can  usually  refer  a  detached  wing 
to  its  proper  genus  and  often  to  its  species,  though  no  less 
than  three  hundred  thousand  species  of  insects  are  already 
known. 

Typically,  there  are  two  pairs  of  wings,  attached  respec- 
tively to  the  mesothorax  and  the  metathorax,  the  prothorax 
never  bearing  wings,  as  was  said.  \\'hen  only  one  pair  is 
present  it  is  almost  invariably  the  anterior  pair,  as  in  Diptera 
and  male  Coccidse,  though  in  male  Stylopidse  it  is  the  posterior 
pair,  the  fore  wnngs  being  rudimentary. 

In  bird  lice,  fieas  and  most  other  parasitic  insects,  the  wnngs 
have  degenerated  through  disuse.  In  Thysanura  and  Collem- 
bola  there  are  no  traces  of  wings  even  in  the  embryo ;  whence 
it  is  inferred  that  wings  originated  later  than  these  orders  of 
insects. 

Miiller  and  Packard  have  regarded  the  wings  as  tergal  out- 
growths; Tower,  however,  has  recently  shown  that  the  wings 
of  Coleoptera,  Orthoptera  and  Lepidoptera  are  pleural  in  ori- 
gin, arising  just  below  the  line  where  later  the  suture  between 
the  pleuron  and  tergum  will  originate,  though  the  wings  may 
subsequently  shift  to  a  more  dorsal  position. 


58  ENTOMOLOGY 

Modifications  of  Wings. — Being  commonly  more  or  less 
triangular,  a  wing  presents  three  margins:  front  (costal), 
outer  (apical)  and  inner  (anal).  Various  modifications  occur 
in  the  front  wings,  which  are  in  many  orders  more  useful  for 
protection  than  for  flight.  Thus,  in  Orthoptera,  they  are 
leathery,  and  are  known  as  tcguiina;  in  Coleoptera  they  are 
usuall}^  horny,  and  are  termed  elytra ;  in  Heteroptera.  the  hase 
of  the  front  wing  is  thickened  and  the  apex  remains  mem- 
branous, forming  a  heinclytron.  Diptera  have,  in  place  of  the 
hind  wings,  a  pair  of  clubbed  threads,  known  as  balancers,  or 
halteres,  and  male  Coccidse  have  on  each  side  a  bristle  that 
hooks  into  a  pocket  on  the  wing  and  serves  to  support  the  lat- 
ter. In  many  muscid  flies  a  doubly  lobed  membranous  squama 
occurs  at  the  base  of  the  wing. 

In  Hymenoptera  the  front  and  hind  wings  of  the  same  side 
are  held  together  by  a  row  of  hooks  (hamuli)  ;  these  are  situ- 
ated on  the  costal  margin  of  the  hind  wing  and  clutch  a  rod- 
like fold  of  the  fore  wing.  In  very  many  moths,  the  two 
wings  are  enabled  to  act  as  one  by  means  of  a  frenulum,  con- 
sisting of  a  spine  or  a  bunch  of  bristles  near  the  base  of  the 
hind  wing,  which,  in  some  forms,  engage  a  membranous  loop 
on  the  fore  wing. 

Venation,  or  Neuration. — A  wing  is  divided  1)y  its  veins, 
or  nervures,  into  spaces,  or  cells.  The  distribution  of  the 
veins  is  of  great  systematic  importance  but.  unfortunately,  the 
homologies  of  the  veins  in  the  different  orders  of  insects  have 
not  been  fixed,  until  recently,  so  that  no  little  confusion  has 
existed  upon  the  subject.  For  example,  the  term  discal  cell, 
used  in  descriptions  of  Lepidoptera,  Diptera,  Trichoptera  and 
Psocid?e,  has  in  no  two  of  these  groups  been  applied  to  the 
same  cell.  The  admirable  work  of  Comstock  and  Needham. 
however,  seems  to  settle  this  disputed  subject.  By  a  study  of 
the  tracheae  which  precede  and,  in  a  broad  way.  determine  the 
positions  of  the  veins,  these  authors  have  arrived  at  a  primi- 
tive type  of  tracheation  (Fig.  67)  to  which  the  more  complex 
types  of  tracheation  and  venation  may  be  referred. 


ANATOMY    AND    PHYSIOLOGY  59 

In  general,  the  following  principal  longitudinal  veins  may 
be  distinguished,  in  the  following  order:  costa,  subcosfa, 
radius,  media,  cubitus  and  aiml  (Figs.  67-71). 


Hypothetical    type   of   venation.     A,   anal    vein;    C,   costa;    Cu,    cubitus;    M,    media;    R, 
radius;    Sc,   subcosta. — Figs.    67-71    after    Comstock    and   Needham. 

The  costa  (C)  strengthens  the  front  margin  of  the  wing 
and  is  essentially  unbranched. 

The  subcosta  (Sc)  is  close  behind  the  costa  and  is  un- 
branched in  the  imagines  of  many  orders  in  which  there  are 
few  wing  veins,  though  it  is  typically  a  forked  vein. 

The  radius  (R),  though  subject  to  much  modification,  is 
typically  five-branched,  as  in  Fig.  67.  The  second  principal 
branch  of  the  radius  is  termed  the  radial  sector  (Rs). 

The  media  (M)  is  often  three-branched  and  is  typically 
four-branched,  according  to  Comstock  and  Needham. 

The  cubitus  (Cu)  has  two  branches. 

The  anal  veins  (A)  are  typically  three,  of  which  the  first 
is  generally  simple,  while  the  second  and  third  are  many- 
branched  in  wings  that  have  an  expanded  anal  area. 

The  Plecoptera,  as  a  whole,  show  the  least  departure  from 
the  primitive  type  of  venation ;  which  is  well  preserved,  also, 
in  the  more  generalized  of  the  Trichoptera. 

Starting  from  the  primitive  type,  specialization  has  occurred 
in  two  ways :  by  reduction  and  by  addition.  Reduction  oc- 
curs either  by  the  atrophy  of  \'eins  or  by  the  coalescence  of 
two  or  more  adjacent  veins.  Atrophy  explains  the  lack  of  all 
but  one  anal  vein  in  RJiypJius  (Fig.  68)   and  other  Diptera, 


6o 


ENTOMOLOGY 


and  the  absence  of  the  base  of  the  media  in  Anosia  (Fig.  69) 
and  many  other  Lepidoptera ;  in  the  pupa  of  Anosia,  the  media 
may  be  found  complete.  Coalescence  "  takes  place  in  two  ways  : 
first,  the  point  at  which  two  veins  separate  occurs  nearer  and 


/St  A  Cu^ 

Wing  of   a   fly,   RliypJitis.     Lettering   as  before. 

nearer  the  margin  of  the  wing,  until  finally,  when  the  margin 
is  reached,  a  single  vein  remains  where  there  were  two  before ; 
second,  the  tips  of  two  veins  may  approach  each  other  on  the 
marsrin  of  the  wing  until  they  unite,  and  then  the  coalescence 


Fig. 


Rl    R2 


2dA 


Wing  of   a   butterfly,   Anc 


Lettering   as   before. 


proceeds  towards  the  base  of  the  wing."  (Comstock  and  Need- 
ham.)  The  former,  or  outward,  kind  of  coalescence  is  com- 
mon in  most  orders  of  insects;  the  latter,  or  inward,  kind  is 
especially  prevalent  in  Diptera. 

Specialization  by  addition  occurs  by  a  multiplication  of  the 
branches  of  the  principal  veins. 


ANATOMY    AND    niYSIOLOGY 


6i 


Comstock  and  Needham  have  succeeded  in  homologizing 
practically  all  the  types  of  neuration,  including  such  perplex- 
ing types  as  those  of  Ephemerida  (Fig.  70),  Odonata  (Fig. 
20,  B)  and  Hymenoptera  (F^ig.  71),  and  their  thorough  work 
affords  a  sound  basis  for  a  rational  terminology  of  the  wing 


igs   of   a    May    fly 


g   as   before. 


veins ;  there  is  no  longer  any  excuse  for  the  lamentable  confu- 
sion that  has  hitherto  attended  the  study  of  venation. 

Folding  of  Wing.^ — In  some  beetles  (as  Chrysobofhris)  the 
wings  are  no  larger  than  the  elytra  and  are  not  folded ;  in 

Fig.  71. 


A   typical   hymenopterous   wing.      Lettering   as   before. 

others,  however,  the  wing's  exceed  the  elytra  in  size,  and  when 
not  in  use  are  folded  under  the  elytra  in  ways  that  are  simple 
but  efficient,  as  described  by  Kolbe  and  by  Tower.  To  be 
understood,  the  process  of  folding  should  be  observed  in  the 
living  insect.     As  described  by  Tower  for  the  Colorado  potato 


02  ENTOMOLOGY 

beetle,  the  folded  wing  (Fig.  72,  B)  exhibits  a  costal  joint 
(a),  a  fold  parallel  to  the  transverse  vein  (b),  and  a  complex 
joint  at  d.  The  wing  rotates  upon  the  articular  head  (ah) 
and  when  folded  back  beneath  the  wing-covers  the  inner 
end  of  the  cotyla   (c)   is  brought  into  contact  with  a  chitin- 

FiG.  72. 


Mh     an 


Wing  of  Leptinotarsa  dccemlincata.  A,  spread;  B,  folded;  a,  costal  joint;  ah, 
articular  head;  an,  anterior  system  of  veins;  b,  transverse  vein;  c,  cotyla;  d,  joint; 
m,  middle  system  of  veins;  p,  posterior  system  of  veins. — After  Tower. 

ous  sclerite  of  the  thorax,  which  stops  the  further  movement 
of  the  cotyla  medianward,  and  as  the  wing  swings  farther  back 
the  middle  system  of  veins  (///)  is  pushed  outward  and  ante- 
riorly. This  motion,  combined  with  the  backward  movement 
of  the  wing  as  a  whole,  produces  the  folding  of  the  distal  end 
of  the  wing.  There  are  no  traces  of  muscles  or  elastic  liga- 
ments in  the  wing  which  could  aid  in  the  folding. 

Mechanics  of  Flight. — The  mechanism  of  insect  flight  is 
much  less  complex  than  one  might  anticipate.  Indeed,  owing 
to  the  structure  of  the  wing  itself,  simple  up  and  down  move- 
ments are  sufiicient  for  the  simplest  kind  of  flight.     During 


ANATOMY    AND    PHYSIOLOGY  63 

oscillation,  the  ])lane  of  the  \vin<;-  changes,  as  may  be  demon- 
strated by  holding"  a  detached  wing  by  its  base  and  blowing  at 
right  angles  to  its  snrface  ;  the  membrane  of  the  wing"  then  yields 
to  the  pressure  of  the  air  while  the  rigid  anterior  margin  does 
not,  to  any  great  extent.  Similarly,  as  the  wing  moves  down- 
ward the  membrane  is  inclined  upward  l)y  the  resistance  of  the 
air,  and  as  the  wing  moves  upward  the  membrane  bends  down- 
ward. Therefore,  by  becoming  deflected,  the  wing  encounters 
a  certain  amount  of  resistance  from 
behind,  which  is  sufficient  to  propel 
the  insect.  The  faster  the  wings  \N\ 
vibrate,  the  greater  t.he  deflection,  \ 
the  greater  the  resistance  from  be- 
hind,  and  the  faster  the  flight  of  the 
insect. 

The    path      traced      in      the      air     bv         Trajectory    of    the    wing    of    an 
.,,.,.  .  '  insect. 

a    rapidly    vibratmg    wmg    may    be 

determined  by  fastening  a  bit  of  gold  leaf  to  the  tip  of  the 
wing  and  allowing  the  insect — a  wasp,  for  example — to  vibrate 
its  wings  in  the  sunlight,  against  a  dark  background.  Under 
these  conditions,  the  trajectory  of  the  wing  appears  as  a  lumi- 
nous elongate  figure  8.  During  flight,  the  trajectory  consists 
of  a  continuous  series  of  these  figures,  as  in  Fig.  73. 

Marey,  the  chief  authority  on  animal  locomotion,  used 
chronophotography,  among  other  methods,  in  studying  the 
process  of  flight,  and  obtained  at  first  twenty,  and  later  one 
hundred  and  ten,  successive  photographs  per  second  of  a  bee 
in  flight.  As  the  wings  were  vibrating  190  times  per  second, 
however,  the  images  evidently  represented  isolated  and  not 
consecutive  phases  of  wing  movement.  Nevertheless,  the 
images  could  be  interpreted  without  difficulty,  in  the  light  of 
the  results  obtained  by  other  methods.  At  length  he  obtained 
sharp  but  isolated  images  of  vibrating  wings  with  an  exposure 
of  only  1/25,000  of  a  second. 

The  frequency  of  wing  vibration  may  be  ascertained  from 
the  note  made  by  the  wing — if  it  vibrates  rapidly  enough  to 


64 


ENTOMOLOGY 


make  one ;  and,  in  any  case,  may  be  determined  graphically  by 
means  of  a  kymograph,  which,  in  one  of  its  forms  consists  of 
a  cylinder  covered  with  smoked  paper  and  revolved  by  clock- 
work at  a  uniform  rate.  The  insect  is  held  in  such  a  position 
that  each  stroke  of  the  wing  makes  a  record  on  the  smoked 
paper,  as  in  Fig.  74. 


Comparing  this  record  with  one  made 


Fig.  74. 


Records  of  wing  vibration.  A,  mosquito,  Anopheles.  Above  is  the  wing  record 
and  below  is  the  record  of  a  tuning  fork  which  vibrated  264.6  times  per  second.  B, 
wasp,  Polistes.     Tlie  tuning  fork  in  this  instance  had  a  vibration  frequency  of  97.6. 

on  the  same  paper  by  a  tuning  fork  of  known  vibration  period, 
the  frequency  of  wing  vibration  can  be  determined  with  great 
accuracy.  As  the  wing  moves  in  the  arc  of  a  circle,  the  radius 
of  which  is  the  length  of  the  wing,  the  extreme  tip  of  the  wing 
records  only  a  short  mark;  if,  however,  the  wing  is  pressed 
against  the  smoked  cylinder,  a  large  part  of  the  figure  8  trajec- 
tory may  be  obtained,  as  in  Fig.  74,  B.  The  wings  of  the  two 
sides  move  synchronously,  as  Marey  found. 

The  smaller  the  wings  are,  the  more  rapidly  they  vibrate. 
Thus  a  butterfly  (P.  rapcc)  makes  9  strokes  per  second,  a 
dragon  fly  28,  a  sphingid  moth  72,  a  bee  190  and  a  house 
fly  330. 

Wing  Muscles. — The  base  of  a  wing  projects  into  the 
thoracic  cavity  and  serves  for  the  insertion  of  the  direct  mus- 
cles of  flight.      Regarding  the  wing  as  a  lever  (Fig.  75,  A), 


ANATOMY    AND    PHYSIOLOGY 


^S 


with  the  fiilcrnni  at  />,  it  is  easy  to  understand  how  the  con- 
traction of  muscle  c  raises  the  wing  and  that  of  muscle  d  low- 
ers it.  These  muscles  are  shown  diagrammatically  in  Fig. 
75.  B.  Besides  these,  there  arc  certain  muscles  of  Ihgiit  which 
act  indirectly  upon  the  wings,  by  altering  the  form  of  the 
thoracic  wall.  Thus 
the  muscle  ic  (Fig.  75, 
B)  elevates  the  wing 
by  pulling  the  tergum 
toward  the  sternum : 
and  the  longitudinal 
muscle  /(/  depresses  the 
wing  indirectly  by 
arching  the  tergum  of 
the  thorax. 

Though  up  and 
down  movements  are 
all  that  are  necessary 
for  the  simplest  kind 
of  insect  flight,  the 
process  becomes  com- 
plex in  proportion  to 
the  efficiency  of  the 
flight.  Thus  in  dragon 
flies  there  are  nine 
muscles  to  each  wing: 
five  depressors,  three 
elevators  and  one  ad- 
ductor. 

Abdomen.  —  The 
chief  functions  of  the 
al)domen  are  respiration  and  reproduction,  to  which  should  be 
added  digestion.  The  abdomen  as  a  whole  has  undergone  less 
differentiation  than  the  thorax  and  presents  a  simpler  and  more 
primitive  segmentation. 

Segments. — A   tvpical  abdominal   segment  bears  a  dorsal 
6 


A,  diagram  to  illustrate  the  action  of  the  wing 
muscles  of  an  insect.  B,  diagram  of  wing  mus- 
cles, a,  alimentary  canal;  en,  muscle  for  con- 
tracting the  thorax,  to  depress  the  wings;  d,  de- 
pressor of  wing;  e,  elevator  of  wing;  ex,  muscle 
for  expanding  the  thorax,  to  elevate  the  wings; 
id,  indirect  depressor;  ie,  indirect  elevator;  /,  leg 
muscle;  p,  pivot,  or  fulcrum;  s,  sternum;  i,  ter- 
gum ;  wg,  wing. — After  Graber. 


66  ENTOMOLOGY 

plate,  or  fergum,  and  a  ventral  plate,  or  sternum,  the  two  being 
connected  by  a  pair  of  pleural  membranes,  which  facilitate  the 
respiratory  movements  of  the  tergum  and  sternum.  Most  of 
the  abdominal  segments  have  spiracles,  one  on  each  side,  situ- 
ated in  or  near  the  pleural  membranes  of  the  first  seven  or 
eight  segments.  The  total  number  of  pairs  of  spiracles  is  as 
follows : 

Thoracic.        Abdominal.  Total. 


Caiiipodca, 
Japyx, 
Mad!  His, 
Lcpisvia, 

3 

4 

O 

7 

7 
8 

3 
II 

9 

10 

Blattidffi.    Acridi 

idae, 

2 

8 

10 

Odonata, 

2 

8 

10 

Heteroptera, 
Lepidoptera, 
Diptera, 

3 

2 

2 

7 
7 
7 

10 

9 
9 

In  most  embryo  insects  there  are  eleven  pairs  of  spiracles 
(three  thoracic  and  eight  abdominal)  ;  in  adults,  howexer,  two 
pairs  are  commonly  suppressed — the  prothoracic  and  the 
eighth  aljdominal. 

Number  of  Abdominal  Segments. — Though  consisting 
typically  of  ten  segments — the  number  evident  in  such  general- 
ized insects  as  Thysanura  and  Ephemerida — eleven  occur  in  va- 
rious adult  Orthoptera.  with  traces  of  a  twelfth,  while  Hey- 
mons  has  detected  twelve  abdominal  segments  in  embryos  of 
Orthoptera  and  Odonata.  In  the  more  specialized  orders,  ten 
may  usually  be  distinguished  with  more  or  less  difficulty, 
though  the  number  is  apparently,  and  in  some  cases  actually 
less,  owing  to  modifications  of  the  base  of  the  abdomen  in 
relation  to  the  thorax,  but  especially  to  modifications  of  the 
extremity  of  the  abdomen,  for  sexual  purposes. 

Modifications. — In  aculeate  Hymenoptera  the  first  segment 
of  the  abdomen  has  been  transferred  to  the  thorax,  where  it 
\?,kno\\md.'s,i\\t  propodcum, or  median  segment;  in  other  words, 
what  appears  to  be  the  first  abdominal  segment  is  actually  the 
second ;  this,  as  in  bees  and  wasps,  often  forms  a  petiole,  which 
enables  the  sting  to  be  applied  in  almost  any  direction.  In  Cy- 
nipidse  the  tergum  of  segment  two  or  three  occupies  most  of  the 


ANATOMY    AND    PHYSIOLOGY 


(V 


the  remaining  segments  being  reduced  and 


llie  terminal  segments  of  the  abdomen  often 


abdominal  ma 
inconspicuous. 

telescope  into  one  another,  as  in 
many  Coleoptera  and  Hymenop- 
tera  (ChrysididcT) .  (ir  undergo 
other  mo<litications  of  form  and 
position  which  obscure  the  seg- 
mentation. As  to  the  number  of 
evident  (not  actual)  abdominal 
segments.  Coleoptera  show  five  or 
six  ventrally  and  seven  or  eight 
dorsally;  Lepidoptera,  seven  in 
the  female  and  eight  in  the  male ; 
Diptera,  nine  (male  Tipulid?e)  or 
only  four  or  five ;  and  Hymenop- 
tera,  nine  (Tenthredinid?e)  or  as 
few  as  three  (Chrysidid?e).  In 
the  larvae  of  these  insects,  how- 
ever, nine  or  ten  abdominal  seg- 
ments are  usually  distinguishable, 
though  the  tenth  is  frequently 
modified,  being  in  caterpillars 
united  with  the  ninth. 

Appendages. — ^Rudimentary  ab- 
dominal limbs  occur  in  Thysanura 
(Machilis,  Fig.  76).  Functional 
abdominal  legs  do  not  occur  in 
adult  insects,  but  in  larv?e  the  ab- 
dominal pro-legs  (often  called  "  false  legs,"  Fig.  64)  are  ho- 
mologous with  the  thoracic  legs  and  the  other  paired  segmental 
appendages,  as  the  embryology  shows.  The  embryo  of  Qican- 
thus,  according  to  Ayers,  has  ten  pairs  of  abdominal  appen- 
dages (Fig.  196),  equivalent  to  the  thoracic  legs.  Most  of 
these  embryonic  abdominal  appendages  are  only  transitory,  but 
the  last  three  pairs  frequently  persist  to  form  the  genitalia,  as  in 


Ventral  aspect  of  the  abdomen 
of  a  female  Machilis  maritima,  to 
show  rudimentary  Hmbs  (a)  of 
segments  two  to  nine.  (The  left 
appendage  of  the  ninth  segment  is 
omitted.)       c,      c,      c,      cerci. — After 

OUDF.MANS. 


68 


ENTOMOLOGY 


Abdomen  of  female  beetle,  Ccraiiibyx,  in 
which  the  last  three  segments  are  used  as  an 
ovipositor. — After    Kolbe. 


Orthoptera  (to  which  order  Qicantluis  l>elongs).  In  Collem- 
bola,  the  embryo  has  paired  abdominal  hml)s,  and  those  of  the 
first  abdominal  segment  eventnally  nnite  to  form  the  peculiar 

I'ciitral  tube  (Fig.  12) 
of  these  insects,  while 
those  of  the  fourth  seg- 
ment form  the  character- 
istic leaping  organ,  or 
////'(■///(/. 

Cerci. — In  many  of  the 
more  generalized  insects, 
the  abdomen  bears  at  its 
extremity  two  or  three 
appendages  termed  ccrci.  These  occur  in  both  sexes  and  are 
frequently  long  and  multiarticulate,  as  in  Thysanura  (Figs. 
76,9,  10)  and  Ephemerida  (Figs.  19, 5;  84), though  shorter  in 
cockroaches  and  reduced  to  a  single  sclerite  in  Acridiidae  (Fig. 
87).  The  paired  cerci,  or  ccrcopoda  of  Packard,  are  usually 
though  not  always  associated  with  the  tenth  abdominal  seg- 
ment and  are  homologous  with  legs,  as  Ayers  has  found  in 
Qicantluis  and  Wheeler  in  Xiphidiiiin.  As  to  their  function. 
the  cerci  of  Thysanura  are  tac- 
tile, and  those  of  the  cockroach 
olfactory,  wdiile  the  cerci  of 
male  Acridiidse  often  serve  to 
hold  the  female  during  copu- 
lation. 

Extremity  of  Abdomen.-^ 
Various  modifications  of  the  terminal  segments  of  the  abdo- 
men occur  for  the  purposes  of  defsecation  and  especially  repro- 
duction. The  anus,  dorsal  in  position,  opens  always  through 
the  last  segment  and  is  often  shielded  above  by  a  suraual  plate 
and  on  each  side  by  a  lateral  plate.  The  genital  orifice  is  al- 
ways ventral  in  position  and  occurs  commonly  on  the  ninth 
abdominal  segment,  though  there  is  some  variation  in  this  re- 
spect. The  external,  or  accessory,  organs  of  reproduction  are 
termed  the  genitalia. 


Fig.  78. 


Abdomen  of  a  female  midge,  Cccido- 
myia  leguminicola,  to  show  the  pseudo- 
ovipositor. 


ANATOMY    AND    PHYSIOLOGY 


69 


Female  Genitalia. — In  Neiiroptera,  Coleoptera,  Lepido])tera 
and  Diptera  the  vagina  simply  opens  to  the  exterior  or  else 
with  the  anus  into  a  common  chamhcr,  or  cloaca.  Often,  as 
in  Ceramhy.x-  (Fig.  yy)  and  Cccidomyia  ( Ing.  /cS)  the  attenu- 

FiG.  79. 


Ovipositor  of  Locust  a.  A,  lateral  aspect;  B,  ventral  aspect;  C,  transverse  section; 
c,  cerci;  d,  dorsal  valve;  i,  inner  valve;  v,  ventral  valve.  The  numbers  refer  to 
abdominal   segments. — After   Kolbe    and   Dewitz. 

ated  distal  segments  of  the  abdomen  serve  the  purpose  of  an 
ovipositor;  thus  in  Cecidomyiid?e,  the  terminal  segments,  tele- 
scoped into  one  another  when  not  in  use,  form  when  extruded 
a  lash-like  organ  exceeding  frequently  the  remainder  of  the 
body  in  length. 

A  true  oz'iposifor  occurs  in  Thysanura,  Orthoptera.  Odo- 
nata,  Hemiptera,  Hymenoptera  and  some  other  orders  of  in- 
sects. The  ovipositor  consists  essentially  of  three  pairs  of 
valves,  or  gonapophyscs — a  dorsal,  a  ventral  and  an  inner 
pair.  The  two  inner  valves  form  a  channel  through  which 
the  eggs  are  conveyed.     In  LocustidcC    (Fig.   79)    the  three 


70 


ENTOMOLOGY 


valves  of  each  side  are  held  together 
by  tongues  and  grooves,  which,  how- 
e\-er,  permit  sliding  movements  to  take 
place.  INIost  authorities  have  found 
that  the  gonapophyses  belong  to  the 
segmental  series  of  paired  appendages 
— are  homodynamous  with  limbs — and 
pertain  commonly  to  abdominal  segments 
seven,  eight  and  nine. 

The  ovipositor  attains  its  greatest 
complexity  in  Hymenoptera,  in  which 
it  becomes  modified  for 
sawing,  boring  or  sting- 
ing. In  Sirc.v  (Fig.  80) 
the  inner  valves  are 
united  together ;  in  Apis 
the  dorsal  valves  are  rep- 

FlG.  82. 


Cross  section  of  the 
ovipositor  of  Sircx.  c, 
channel;  d,  d,  dorsal 
valves;  i,  united  inner 
valves;  v,  v,  ventral 
valves. — After    Taschen- 

BERG. 


Fig.  81. 


Sting  and  poison,  apparatus 
of  honey  bee.  ag,  accessory 
gland;  p,  palpus;  pg,  poison 
gland  (formic  acid) ;  r,  reser- 
voir;    .?,     sting. — After     Kraepe- 


Sting  of  honey  bee.  A,  i,  2,  .?,  positions 
in  three  successive  thrusts;  s,  sheath.  B, 
cross  section;  c,  channel;  /,  united  inner 
valves,  forming  the  sheath;  .',  '',  ventral 
valves,  or  darts. — A,  after  Cheshire;  B,  after 
Fencer. 

resented  by  a  pair  of  palpi,  the 
inner  valves  unite  to  form  the 
sheath  (Fig.  8i,  B),  and  the  ven- 
tral two  form  the  darts,  each  of 
which  has  ten  barbed  teeth  behind 
its  apex,  which  tend  to  prevent 
the  withdrawal  of  the  sting  from  a 
wound.     The  action  of  the  sting,  as 


ANATOMY    AND    PHYSIOLOGY 


71 


described  by  Cheshire,  is  rather  complex.      Brielly,  the  sheath 

serves  to  open  a  wound  and  to  guide  the 

darts ;   these   strike  in   ahernately,   inter- 
rupted at  intervals  by  the  deeper  pknig- 

ing-  of   the   sheath    ( h^ig".   81,   A).     The 

poison  of  the  hone}'  l:)ee   is   secreted   l^y 

two  glands,  one  acid  and  the  other  alka- 
line.    The  former  (Fig.  82)  consists  of 

a  glandular  region  which  secretes  formic 

acid,    of    a    reservoir,    and    a    duct    that 

empties  its  contents  into  the  channel  of 

the    sheath.       The    alkaline    gland    also 

opens  into  the  reser\-oir.      It  is  said  that 

both   fluids   are    necessary    for   a    deadly 

effect;  and  that  in  insects  which  simply 

paralyze  their  prey,  as  the  solitary  wasps, 

the  alkaline  glands  are  functionless. 
Male    Genitalia. — The   poiis  may   be 

hollow  or  else  solid,  and  in  the  latter  case 

the  contents  of  the  ejaculatory  duct  are 

spread  upon  its  surface.  Morphologically,  the  male  gona- 
pophyses  correspond  to  those  of  the 
female.  The  penis  (Fig'.  83)  rep- 
resents the  two  inner  valves  of  the 
ovipositor  and  is  frequently  enclosed 
by  one  or  two  pairs  of  valves.  In 
Ephemerida  the  two  inner  valves 
are  partly  or  entirely  separate  from 
each  other,  forming  two  intromit- 
tent  organs  (Fig.  84). 

In  male  Odonata,  the  ejaculatory 
duct  opens  on  the  ninth  abdominal 
segment,  but  the  copulatory  organ  is 
placed  on  the  under  side  of  the  sec- 
ond segment,  to  which  the  spermato- 
zoa are  transferred  by  the  bending 

of  the  abdomen.     At  copulation,  the  abdominal  claspers  of  the 


cniity  of  abdomen 
of  a  male  beetle,  Hy- 
drophilus,  ventral  aspect. 
g,  genitalia;  p,  penis; 
Z'^,  v^,  pairs  of  valves 
enclosing  tbe  penis;  6-9, 
sterna  of  abdominal  seg- 
ments.— After    KoLBE. 


Extremity    of    abdomen  of    i 

male   May   fly,   Hexagenia  z'aria 

bills,    ventral    aspect.       c,  c,     c 

cerci;    cl,    cl,    claspers;    i,  i,    in 
tromittent    organs. 


72 


ENTOMOLOGY 


male  grasp  the  neck  of  the  female,  and  the  latter  bends  her 
abdomen  forward  nntil  the  tip  reaches  the  peculiar  copulatory 
apparatus  of  the  male. 

Fig.  8s. 


Genitalia  of  a  moth,  Samia  cecropia.  A,  male;  B,  female;  a,  anus;  c,  c,  claspers; 
o,  opening  of  common  oviduct;  p,  penis;  s,  uncus  (the  doubly  hooked  organ);  v,  vesti- 
bule, into  which  the  vagina  opens.      The  numbers  refer  to   abdominal   segments. 

The  claspers  of  the  male  consist  of  a  single  pair,  variously- 
formed.  They  are  present  in  Ephemerida,  Neuroptera.  Tri- 
choptera,  Lepidoptera  (Fig.  85),  Diptera  and  some  Hymen- 
optera,  though  not  in  Coleoptera,  and  often  afford  good  spe- 
cific characters,  a§  in  Odonata. 

Fig.  86. 


B 


Terminal  abdominal  appendages  of  a  dragon  fly,  Plathemis  trimaculata.  A,  male; 
B,  female.  i,  inferior  appendage;  s,  s,  superior  appendages  (cerci).  The  numbers 
refer  to    abdominal   segments. 

Thanaos,  the  claspers  are  peculiar  in  being  strongly  asym- 
metrical. In  Odonata  (Fig.  86,  A)  and  Orthoptera  (Fig. 
87,  A)  the  cerci  of  the  male  often  serve  as  claspers. 


ANATOMY    AND    PHYSIOLOGY 


73 


In  many  insects  the  tergum  of  the  last  alxloniinal  segment 
forms  a  small  siiraiial  plate  (Fig.  87,  B,  sp)  ;  this  sometimes 


Fig.  87. 


8g    10    u 


9  10      n 


Extremity  of  the  abdomen  of  a  grasshopper,  Melanoplus  diffcrcntialis.  A,  male; 
B,  female.  The  terga  and  sterna  are  numbered,  c,  cercus;  d,  dorsal  valves  of  ovi- 
positor; e,  egg  guide;  p,  podical  plate;  s,  spiracle;  sp,  suranal  plate;  7',  ventral  valves 
of  ovipositor. 


supplements  the  claspers  of  the  male 
Lepidoptera  (Fig.  85,  A,  s). 


heir  function,  as  in 


2.   Integument 

Insects  excel  all  other  animals  in  respect  to  adaptive  modi- 
fications of  the  integument.  No  longer  a  simple  limiting 
membrane,  the  integument  has  become  hardened  into  an  exter- 
nal skeleton,  evaginated  to  form  manifold  adaptive  structures 
such  as  hairs  and  scales,  and  invaginated,  along  with  the  un- 
derlying cellular  layer,  to  make  glands  of  various  kinds. 

Chitin. — The  skin,  or  cuticula,^  of  an  insect  differs  from 
that  of  a  worm,  for  example,  in  being  thoroughly  permeated 
with  a  peculiar  substance  known  as  chitin — the  basis  of  the 
arthropod  skeleton.  This  is  a  substance  of  remarkable  sta- 
bility, for  it  is  unaffected  by  almost  all  ordinary  acids  and 
alkalies,  though  it  is  soluble  in  sodic  or  potassic  hypochlorite 
(respectively,  Eau  de  Labarraque  and  Eau  de  Javelle)  and 
yields  to  boiling  sulphuric  acid.  If  kept  for  a  year  or  so 
under  water,   however,   chitin  undergoes   a   slow  dissolution, 

^  The  cuticida  of  an  insect  should  be  distinguished  from  the  cuticle  of 
a  vertebrate,  the  former  being  a  hardened  fluid,  while  the  latter  consists 
of  cells  themselves,  in  a  dead  and  flattened  condition. 


74 


ENTOMOLOGY 


possibly  a  putrefaction,  which  accounts  in  a  measure  for  the 
rapid  disappearance  of  insect  skeletons  in  the  soil  (Miall  and 
Denny).  By  boiling  the  skin  of  an  insect  in  potassic  hydrate 
it  is  possible  to  dissolve  away  the  cuticular  framework,  leav- 
ing fairlv  pure  chitin,  without  destroying  the  organized  form 
of  the  integument,  though  less  than  half  the  weight  of  the 
integument  is  due  to  chitin.  The  formula  of  chitin  is  given 
as  CgHisNOu  or  CisHigNOig  by  Krukenberg,  and  Packard 
adopts  the  formula  CisHgeNgOjo;  though  no  two  chemists 
agree  as  to  the  exact  proportions  of  these  elements,  owing 

probably   to   variations    in    the 

Fir    88 

substance  itself  in  different  in- 
sects or  even  in  the  same  species 
of  insect.  Iron,  manganese 
and  certain  pigments  also  enter 
into  the  composition  of  the 
integument. 

Chitin  is  not  peculiar  to  ar- 
thropods, for  it  has  been  de- 
tected in  the  setae  and  pharyn- 
geal teeth  of  annelid  worms, 
the  shell  of  Lingula  and  the 
pen  of  the  cuttle  fish  (Kruken- 
berg). 

The  chitinous  integument  (Fig.  88)  of  most  insects  con- 
sists of  two  layers :  ( i )  an  outer  layer,  homogeneous,  dense, 
without  lamellae  or  pore  canals,  and  being  the  seat  of  the  cutic- 
ular colors;  (2)  an  inner  layer,  "thickly  pierced  with  pore 
canals,  and  always  in  layers  of  different  refractive  indices  and 
different  stainability."  (Tower.)  These  two  layers,  respec- 
tively primary  and  secondary  cuticula,  are  radically  different 
in  chemical  and  physical  properties.  The  chitinous  cuticula 
is  secreted,  as  a  fluid,  from  the  hypodermis  cells.  Each  layer 
arises  as  a  fluid  secretion  from  the  hypodermis  cells,  the  pri- 
mary cuticula  being  the  first  to  form  and  harden. 

The  fluid  that  separates  the  old  from  the  new  cuticula  at 


-  h 


Section  through  integument  of  a 
beetle,  Chrysobothris.  b,  basement 
membrane;  c^,  primary  cuticula;  c", 
secondary  cuticula;  h,  hypodermis  cell; 
n,    nucleus. — After   Tower. 


ANATOMY    AND    PHYSIOLOGY 


75 


ecdysis  is  poured  over  the  liypoderniis  In-  eertain  large  special 
cells,  which,  according  to  Tower,  "are  not  true  glands,  but 
the  setigerous  cells  which,  in  early  life,  are  chiefly  concerned 
with  the  formation  of  the  hairs  upon  the  body;  but  upon  the 

Fig.  89. 


s 


Modifications  of  the  hairs  of  bees 
D,    Chclostoim 


A,  B,   Mcgachile;  C,   E,  F,   Collates, 
-After    Saunders. 


loss  of  these,  the  cell  takes  on  the  function  of  secreting  the 
exuvial  fluid,  which  is  most  copious  at  pupation.  These  cells 
degenerate  in  the  pupa,  and  take  no  part  in  the  formation  of 
the  imaginal  ornamentation." 

Histology. — The  chitinous  cuticula  owes  its  existence  to 
the  activity  of  the  underlying  layer  of  hypodermis  cells  (Fig. 
88).  These  cells,  distinct  in  embryonic  and  often  in  early  lar- 
val life,  subsecjuently  become  confluent  by  the  disappearance  of 
the  intervening  cell  walls,  though  each  cell  is  still  indicated  by 
its  nucleus.  The  cells  are  limited  outwardly  by  the  cuticula 
and  inw^ardly  by  a  delicate,  hyaline  bascinciit  inciiibrauc;  they 
contain  pigment  granules,  fat-drops,  etc. 

Externally  the  cuticula  may  be  smooth,  wrinkled,  striate, 
granulate,  tuberculate,  or  sculptured  in  numberless  other 
ways ;  it  may  be  shaped  into  all  manner  of  structures,  some 
of  which  are  clearly  adaptive,  while  others  are  unintelligible. 


76 


ENTOMOLOGY 


Fig.  go. 


Hairs,  Setae  and  Spines. — These  occur  universally,  serv- 
ing a  great  variety  of  purposes ;  they 
are  not  always  simple  in  form,  but  are 
often  toothed,  branched  or  otherwise 
modified  (Fig.  89).  Hairs  and  bris- 
tles are  frequently  tactile  in  function, 
over  the  general  integument  or  else 
locally;  or  olfactory,  as  on  the  antennae 
of  moths;  or  occasionally  auditory,  as 
on  the  antennae  of  the  male  mosquito; 
these  and  other  sensory  modifications 
are     described     beyond.       The     hairy 


Section  of  antenna  of  a 
moth,  Saturnia,  to  show 
developing  hairs,  c,  cutic- 
ula;  f,  formative  cell  of 
hair;  h,  hypodermis;  t, 
trachea. — After    Semper. 


pillars  (as  Isia  isahcUa)  probably  pro- 
tects them  from  sudden  changes  of 
temperature.  Hairs  and  spines  fre- 
quently protect  an  insect  from  its  ene- 
mies, especially  when  these  structures 
and    emit    a 


Fig.  91. 


are    glandular 

malodorous,  nauseous  or 
irritant  fluid.  Glandular 
hairs  on  the  pulvilli  of 
many  flies,  beetles,  etc., 
enable  these  insects  to  walk 
on  slippery  surfaces.  The 
twisted  or  branched  hairs 
of  bees  serve  to  gather 
and  hold  pollen  grains ;  in 
short,  these  simple  struc- 
tures exhibit  a  surprising 
variety  of  adaptive  modifica- 
tions, many  of  which  \\\\\  be 
described  in  connection  with 
other  subjects. 

A     hair     arises     from     a 
modified  hypodermis  cell    (Fig.   90),   the  contents  of   which 


Radial     section     through     the    base  of    a 

hair  of  a  caterpillar,  Picris  rapcr.     c,  cutic- 

ula;    /,    formative    cell;    h,    hair;    hy,  hypo- 
dermis. 


ANATOMY    AND    PHYSIOLOGY 


77 


extend  through  a  pore  canal  into  the  interior  of  the  liair  (Fig. 
91  )  ;  sometimes,  to  be  sure,  as  in  glandular  or  sensory  hairs, 
the  hair  cell  is  multinucleate,  rep- 
resenting, therefore,  as  many  cells 
as  there  are  nuclei.  The  wall  nf 
a  hair  is  continuous  witli  the  gen 
eral  cuticula  and  at  moulting  each 
hair  is  stripi)ed  ofT  with  the  rest 
of  the  cuticula,  leaving  in  its  place 
a  new  hair,  which  has  been  form- 
ings inside  the  old  one. 

Scales.  —  Besides  occurring 
thrcaighout  the  order  Lepidoptera 
and  in  numerous  Trichoptera. 
scales  are  found  in  many  Thys- 
anura  and  Collembola.  several 
families  of  Coleoptera  (including 
DermestidcC  and  Curculionidre),  a 
few  Diptera  and  a  few  Psocidie. 

Though  diverse  in  form  (Fig. 
92),  scales  are  essentially  flattened 
sacs  having  at  one  end  a  short 
pedicel  for  attachment  to  the  in- 
tegument. The  scales  usuallv  bear  markings,  which  are 
more  or  less  characteristic  of  the  species ;  these  markings, 
always  minute,  are  in  some  species  so  exquisitely  fine  as 
to    test    the    highest    powers    of    the    microscope ;    the    scales 

of    certain    Collembola    {Lchi- 

Fif-.    03 

docyrtiis.  etc. )  have  long  been 
used,  under  the  name  of 
"  Podura  "  scales,  to  test  the 
resolving  power  of  objec- 
tives, for  which  purpose  they 
are  excelled  only  by  some  of  the  diatoms.  Butterfly  scales 
are  marked  with  ])arallel  longitudinal  ridges  (Fig.  92,  C), 
which    are    confined    almost    entirely    to    the    upper,    or    ex- 


X'arious  forms  of  scales. 
A,  E,  thysanuran,  Machilis;  B, 
beetle,  Anthrcnus;  C,  butterfly, 
Pic'-is:   D.    moth,    Limacodes. 


Cross    section    of    scale    of    Aiiosia. — 
After    Mayer. 


78 


ENTOMOLOGY 


posed,    surface    of    the    scale    (Fig.    93)    and    number    from 
^;^  or  less   (Anosia)   to   1,400    (MorpJio)   to  each  scale,  the 

_  strise    being-    from    .002    mm. 

Fig.  94.  ^ 

to  .0007  mm.  apart  (Kel- 
logg) ;  between  these  longi- 
tudinal ridges  may  be  dis- 
cerned delicate  transverse 
markings.  Internally,  scales 
are  hollow  and  often  contain 
pigments  derived  from  the 
blood. 

On  the  wing  of  a  butter- 
fly the  scales  are  arranged 
in  regular  rows  and  overlap 
one  another,  as  in  Fig.  94; 
in  the  more  primitive  moths 
and  in  Trichoptera.  how- 
Arrangement  of  scales  on  the  wing  of  a  evcr,     their     distribution     is 

butterfly,     Papilio.  .  .  , 

rather  irregular. 

A  scale  is  the  equivalent  of  a  hair,  for  (i)  a  complete  series 

of  transitions  from  hairs  to  scales  may  be  found  on  a  single 

individual  (Fig.  95)  ;  and  (2)  hairs  and  scales  agree  in  their 

manner  of  development,  as  shown  by  Semper,  Schaffer,  Spu- 

Fi 


Hairs  and   scales  of   a  moth,   Sa)nia   cccropia. 

ler,  Mayer  and  others.  Both  hairs  and  scales  arise  as  pro- 
cesses from  enlarged  hypodermis  cells,  or  formative  cells  (Fig. 
96).  The  scale  at  first  contains  protoplasm,  which  gradually 
withdraws, 
membranes  of  the  scale  together. 


ANATOMY    AND    PHYSIOLOGY 


79 


Uses  of  Scales. — Anions^-  Tliysaniira  and  C"<)11cnil)c)la.  scales 
occur  (Mily  on  such  species  as  live  in  comparatively  drv  situa- 
tions, from  which  it  may  be  inferred  that  tlie  scales  serve  to 
retard  the  evaporation  of  moisture  through  tlie  delicate  integu- 
ment of  these  insects.     This  inference  is  supported  by  the  fact 

Fig.  96.  Fk;.  97. 


Development  of  butterfly  scales. 
A,  I'anessa;  B,  Anosia.  b,  base- 
ment membrane;  f,  formative  cell; 
h,  hypodermis;  s,  scale. — After 
Mayer. 


Androconia  of  butter- 
flies. A,  Pieris  rapa;  B, 
Everes  comyntas. 


that  none  of  the  scaleless  Collembola  can  live  long  in  a  dry 
atmosphere ;  they  soon  shrivel  and  die  even  under  conditions 
of  dryness  which  the  scaled  species  are  able  to  withstand.  In 
Lepidoptera  the  scales  are  possibly  of  some  value  as  a  mechan- 
ical protection;  they  have  no  influence  upon  flight,  as  Mayer 
has  proved,  and  appear  to  be  useful  chiefly  as  a  basis  for  the 


8o 


ENTOMOLOGY 


development  of  color  and  color  patterns — which  are  not  infre- 
cjuently  adaptive. 

Androconia. — The  males  of  many  butterflies,  and  the  males 
only,  have  peculiarly  shaped  scales  known  as  androconia  (Fig. 
97)  ;  these  are  commonly  confined  to  the  upper  surfaces  of  the 
front  wings,  where  they  are  mingled  with  the  ordinary  scales 
or  else  are  disposed  in  special  patches  or  under  a  fold  of  the 

costal  margin  of  the  wing 
(Thanaos) .  The  characteris- 
tic odors  of  male  butterflies 
have  long  been  attributed  to 
these  androconia  and  M.  B. 
Thomas  has  found  that  the 
scales  arise  from  glandular 
cells,  which  doubtless  secrete 
a  fluid  that  emanates  from 
the  scale  as  an  odorous  va- 
por, the  evaporation  of  the 
fluid  being  facilitated  l)y  the 
spreading  or  branching  form 
of  the  androconium.  Similar 
scales  occur  also  on  the  wings  of  various  moths  and  some 
Trichoptera  (Mystacidcs) . 

Glands. — A  great  many  glands  of  various  form  and  func- 
tion have  been  found  in  insects.  Most  of  these,  being  formed 
from  the  hypodermis,  may  logically  be  considered  here,  ex- 
cepting some  which  are  intimately  concerned  with  digestion 
or  reproduction. 

Glandular  Hairs  and  Spines. — The  presence  of  adhesive 
hairs  on  the  empodium  of  the  foot  of  a  fly  enables  the  insect 
to  walk  on  a  smooth  surface  and  to  walk  upside  down ;  these 
tcnent  hairs  emit  a  transparent  sticky  fluid  through  minute 
pore  canals  in  their  apices.  The  tenent  hairs  of  Hylobius 
(Fig.  98)  are  each  supplied  with  a  flask-shaped  unicellular 
gland,  the  glutinous  secretion  of  which  issues  from  the  bulbous 


Section  across  tarsus  of  a  beetle, 
Hylobius,  to  show  bulbous  glandular 
hairs. — After    Simmermacher. 


ANATOMY    AND    PHYSIOLOGY 


8l 


Fig.  99. 


Stinging  hair  of  a  caterpillar, 
Gastropacha.  c,  cuticula;  g, 
gland  cell;  h,  hair;  hy,  hypo- 
dermis. — After   Claus. 


extremity  of  the  hair.     Bulbous  tenent  hairs  occur  also  on  the 
tarsi  of  Collembola,  AphididcT  and  other  insects. 

Nettling-  hairs  or  spines  clothe  the 
caterpillars  of  certain  Satuniiidae 
{  Autoiucris) ,  Liparichc.  etc.  These 
spines  ( h'ig.  99),  which  are  sharp, 
brittle  and  tilled  \\ith  poison.  Ijreak 
to  pieces  when  the  insect  is  handled 
and  cause  a  cutaneous  irritation 
much  like  that  made  by  nettles.  In 
Lagoa  crispata  (Fig-.  100)  the  irri- 
tating fluid  is  secreted,  as  is  usual, 
by  several  large  hypodermal  cells 
at  the  base  of  each  spine.  These 
irritating  hairs  protect  their  pos- 
sessors from  almost  all  birds  except 
cuckoos. 

Repellent  Glands. — The  various 
offensive    fluids   emitted   by   insects 

are  also  a  highly  effective  means  of  defence  against  birds 
and  other  insectivorous  vertebrates  as  well  as  against  preda- 
ceous  insects.  The  blood  itself  serves 
as  a  repellent  fluid  in  the  oil-beetles 
(Meloidcc)  and  CoccinellicLne,  issuing  as 
a  yellow  fluid  from  a  pore  at  the  end 
of  the  femur.  The  blood  of  MeloidcT 
( one  species  of  which  is  still  used  me- 
dicinally under  the  name  of  "  Spanish 
Fly  '■)  contains  cantharidine,  an  ex- 
tremely caustic  substance,  which  is  an 
almost  perfect  protection  against  birds, 
reptiles  and  predaceous  insects.  Coccinel- 
lid?e  and  Lampyridie  are  similarly  exempt 
from  attack.  Larvae  of  Cimhcx  when 
disturbed  squirt  jets  of  a  watery  fluid 
from  glands  opening  above  the  spiracles.  Many  Carabidse 
eject  a  pungent  and  often  corrosive  fluid  from  a  pair  of  anal 
7 


Fig.   100. 


Stinging  spines  of 
caterpillar,  Lagoa  c 
pata. — After    P..\ck.\rd. 


82  ENTOMOLOGY 

glands  (Fig.  146)  ;  this  fluid  in  Brachinus,  and  occasionally 
in  Galerita  janns  and  a  few  other  carabids,  volatilizes  explo- 
sively upon  contact  with  the  air.  When  one  of  these  "  bom- 
bardier-beetles "  is  molested  it  discharges  a  puff  of  vapor, 
accompanied  by  a  distinct  report,  reminding  one  of  a  minia- 
ture cannon,  and  this  performance  may  be  repeated  several 
times  in  rapid  succession;  the  vapor  is  acid  and  corrosive, 
staining  the  human  skin  a  rust-red  color. 
Individuals  of  a  large  South  American 
Brachinus  when  seized  "  immediately 
began  to  play  off  their  artillery,  burning 
and  staining  the  flesh  to  such  a  degree 
that  only  a  few  specimens  could  be  cap- 
tured with  the  naked  hand,  leaving  a 
mark  which  remained  for  a  considerable 
time."      (Westwood.) 

As  malodorous  insects,  Hemiptera  are 

Osmeterium    of   Pajyilio  UOtOrioUS,     thougll     UOt     2.     fcW     hcmiptC- 

polyxenes.  /  .    r  .1      • 

rous  odors  are  (apart  from  tlien^  associa- 
tions) rather  agreeable  to  the  human  olfactory  sense.  Com- 
monly the  odor  is  due  to  a  fluid  from  a  mesothoracic  gland  or 
glands,  opening  between  the  hind  coxae. 

Eversible  hypodermal  glands  of  many  kinds  are  common  in 
larvae  of  Coleoptera  and  Lepidoptera.  The  larvae  of  Mclasoma 
lapponica,  among  other  Chrysomelidae.  evert  numerous  paired 
vesicles  which  emit  a  peculiar  odor.  The  caterpillars  of  our 
Popiliu  butterflies,  upon  being  irritated,  evert  from  the  pro- 
thorax  a  yellow  Y-shaped  osmeterium  (Fig.  loi)  which  dif- 
fuses a  characteristic  but  indescribable  odor  that  is  probably 
repellent.  The  larva  of  Cerura  everts  a  curious  spraying 
apparatus  from  the  under  side  of  the  neck. 

Alluring  Glands. — Odors  are  largely  used  among  insects  to 
attract  the  opposite  sex.  The  androconia  of  male  butterflies 
have  already  been  spoken  of.  Males  of  Catocala  concumhens 
disseminate  an  alluring  odor  from  scent  tufts  on  the  middle 
legs.     Female  saturniid  moths    (as  eecropia  and  promcthca) 


ANATOMY    AND    PHYSIOLOGY 


83 


entice  the  males  by  means  of  a  characteristic  odor,  emanating 
from  the  extremity  of  the  alxlonien.  In  lyca^nid  caterpillars, 
an  eversible  sac  on  the  dorsum  of  the  seventh  abdominal  seg- 
ment secretes  a  sweet  tlnid.  for  the  sake  of  which  these  larvae 
are  sought  out  by  ants. 

Wax  Glands. — Wax  is  secreted  by  insects  of  several  orders, 
but  especially  Hymenoptera  and  Hemiptera.     In  the  worker 


\'entral    aspect    of   worker    honey    bee,    showing   the    four    pairs   of    wax    scales. — After 
Cheshire. 

honey  bee  the  wax  exudes  from  unicellular  hypodermal  glands 
and  appears  on  the  under  side  of  the  abdomen  as  four  pairs 
of  wax  scales  (Fig.  102).  Plant  lice  of  the  genus  Schizo- 
nciira  owe  their  woolly  appearance  to  dense  white  filaments  of 
wax,  which  arise  from  glandular  hypodermal  cells.  In  scale 
insects,  waxen  threads,  emerging  from  cuticular  pores,  become 
matted  together  to  form  a  continuous  shield  over  and  often 
under  the  insect  itself,  the  cast  skins  often  being  incorporated 
into  this  waxen  scale.  The  wax  glands  in  Coccid?e  are  simply 
enlarged  hypodermis  cells. 

Silk  Glands. — Larv?e  of  very  diverse  orders  spin  silk,  for 
the  purpose  of  making  cocoons,  w-ebs,  cases,  and  supports  of 
one  kind  or  another.  Silk  glands,  though  most  characteristic 
of  Lepidoptera  and  Trichoptera,  occur  also  in  the  cocoon- 
spinning  larvre  of  not  a  few  Hymenoptera  (saw  flies,  ichneu- 
mons, wasps,  bees,  etc.),  in  Diptera  (Cecidomyiidse),  Neurop- 


ENTOMOLOGY 


tera    (Chrysopidse,    Myrmeleonidse),    and    in    various    larvae 
whose  pup?e  are  suspended  from  a  silken  support,  as  in  the 

coleopterous  families  Coc- 
cinellidae  and  Chrysomel- 
idse  (in  part)  and  the  dip- 
terous family  Syrphid?e, 
as  well  as  most  diurnal 
Lepidoptera. 

Fig.  104. 


Head  of  caterpillar  of  Samia  cecropia.  a, 
antenna;  c.  clypeus;  /,  labrura;  Ip,  labial  palpus; 
m,  mandible;  mp,  maxillary  palpi;  o,  ocelli;  s, 
spinneret. 

The  silk  glands  of  caterpillars 
are  homologous  with  the  true 
salivary  glands  of  other  insects, 
opening  as  usual  through  the  hy- 
popharynx,  which  is  modified  to 
form  a  spinning  organ,  or  spin- 
ncrct  (Fig.  103).  The  silk  glands 
of  Lepidoptera  are  a  pair  of  long 
tubes,  one  on  each  side  of  the 
body,  but  often  much  longer  than 
the  body  and  consequently  convo- 
luted. Thus  in  the  silk  worm 
{Bouihyx  inori)  they  are  from 
four  to  five  times  as  long  as  the 
body    and    in    Tclca    polyphenius, 


Silk  glands  of  the  silk  worm, 
Bombyx  inori.  cd,  common  duct; 
d,  one  of  the  paired  ducts;  g,  g, 
Filippi's  glands;  gl,  gland  proper; 
p,  thread   press;   r,   reservoir. 


worm    the    convoluted    glandular 

portion  of  each  tube  (Fig.  104)  opens  into  a  dilatation,  or  silk 

reservoir,  which  in  turn  empties  into  a  slender  duct,  and  the 


ANATOMY    AND    PHYSIOLOGY 


85 


Fig.  105. 


B 


two  ducts  join  into  a  short  common  duct,  which  passes 
tlirough  the  tuluilar  spinneret.  Two  divisions  of  the  spinning 
tube  are  distinguished:  (i)  a  posterior  muscular  i)ortion,  or 
thread-press  and  (2)  an  anterior  directing  tube.  The  thread- 
press  combines  the  two  streams  of 
silk  fluid  into  one,  determines  the  form 
of  the  silken  thread  and  arrests  the 
emission  of  the  thread  at  times,  besides 
having  other  functions.  Tlie  silk  fluid 
hardens  rapidly  upon  exposure  to  the 
air;  about  fifty  per  cent,  of  the  fluid 
is  actual  silk  substance  and  the  re- 
mainder consists  of  protoplasm  and 
gum,  with  traces  of  wax,  pigment,  fat 
and  resin. 

A  transverse  or  radial  section  of  a 
silk  gland  shows  a  layer  of  glandular 
epithelial  cells,  with  the  usual  intima 
and  basement  membrane  (  Fig.  105  )  : 
the  cells  are  remarkably  large  and  their 
nuclei  are  often  branched ;  the  intima 
is  distinctly  striated,  from  the  presence 
of  pore-canals.  The  glands  arise  as 
evaginations  of  the  pharynx  (ectoder- 
mal )  and  the  chitinous  intima  of  each 
gland  is  cast  at  each  moult,  along  with 
the  general  integument. 

The  silk  glands  of  Trichoptera  are  essentially  like  those  of 
Lepidoptera,  but  the  glands  of  Chrysopa,  Mynneleon,  Coc- 
cinellidce,  Chrysomelid?e  and  Syrphid?e,  which  open  into  the 
rectum,  are  morphologically  quite  different  from  those  of 
Lepidoptera. 

3.  Muscular  System 

The  number  of  muscles  possessed  by  an  insect  is  surpris- 
ingly large.  A  caterpillar,  for  example,  has  about  two 
thousand. 


Sections  of  silk  gland  of 
the  silk  worm.  A,  radial; 
B,  transverse,  h,  basement 
membrane;  i,  intima;  s, 
glandular  cell  with  branched 
nucleus. — After   Helm. 


86 


ENTOMOLOGY 


The  muscles  of  the  trunk  are  segmentally  arranged — most 
evidently  so  in  the  body  of  a  larva  or  the  abdomen  of  an 
imago,  where  the  musculature  is  essentially  the  same  in  sev- 
eral successive  segments.  In  the  thoracic  segments  of  an  ima- 
go, however,  the  musculature  is,  at  first  sight,  unlike  that  of 


Fig.  io8. 


Muscles  of  cockroach;  of  ventral,  dorsal  and  lateral  walls,  respectively,  a,  alary 
muscle;  ahc,  abductor  of  coxa;  adc,  adductor  of  coxa;  ef,  extensor  of  femur;  h,  head 
muscles;  Is,  longitudinal  sternal;  It,  longitudinal  tergal;  Ith,  lateral  thoracic;  os, 
oblique  sternal;  ot,  oblique  tergal;  ts,  tergo-sternal;  ts^,  first  tergo-sternal. — After 
MiALL   and   Denny. 


the  abdomen,  and  in  the  head  it  is  decidedly  different ;  though 
future  studies  will  doubtless  show  that  the  thoracic  and  cepha- 
lic kinds  of  musculature  are  only  modifications  of  the  simpler 
abdominal  type — modifications  brought  about  in  relation  to 
the  needs  of  the  legs,  wings,  mouth  parts,  antenncT  and  other 
movable  structures. 

The  muscular  system  has  been  generally  neglectetl  by  stu- 
dents of  insect  anatomy ;  the  only  comprehensive  studies  upon 
the  subject  being  those  of  Straus-Diirckheim  (1828)  on  the 
beetle  Melolontha;  Lyonet  (1762),  Newport  (1834)  and 
Lubbock  (1859)  on  caterpillars;  and  the  more  recent  studies 
of  Lubbock  and  Janet  on  Hymenoptera. 


ANATOMY    AND    PHYSIOLOGY 


87 


scle    fiber    of 
an   insect. 


The  more  important  muscles  in  the  body  of  a  cockroach  are 
represented  in  l'"ii;s.  106-108,  from  Miall  and  Denny.  The 
longitudinal  stcrnals  with  the  longitudinal  tcrgals  act  to  tele- 
scope the  abdominal  see-ments ;  the  oblique  , 

i  '^  -'  ]  K    109 

stcrnals  l)en(l  the  alxlomen  laterall}- ;  the 
tcrgo-stcrnals,  or  \ertical  expiratory  mus- 
cles, draw  the  tergum  and  sternum  to- 
gether. The  muscles  of  the  legs  and  the 
wings  have  already  been  referred  to. 

Structure  of  Muscles. — The  muscles 
of  insects  differ  greatly  in  form  and  are 
inserted  frequently  by  means  of  chitinous 
tendons.  A  muscle  is  a  bundle  of  long- 
fibers,  each  of  which  has  an  outer  elastic  striated 
membrane,  or  sarcolcninta,  within  which 
are  several  nuclei ;  thus  the  fiber  represents  several  cells, 
wdiich  have  become  confluent.  With  rare  exceptions  ("  alary  " 
muscles   and    possibly   a    few    thoracic   muscles)    the    muscle 

fibers  of  an  insect  present 
j^l  a  striated  appearance,  owing 
to  alternate  light  and  dark 
bands  (Fig.  109),  the  for- 
mer being  singly  refracting, 
or  isotropic,  and  the  latter 
doubly  refracting,  or  aniso- 
tropic. 

The   minute   structure   of 
these  fibers,  being  extremely 

Minute    structure    of    a    striated   muscle  difflCUlt        of        interpretation, 

fiber.     A,    longitudinal    section;    B,    trans-  .                 . 

verse  section  in  the  region  of  /;  C.  trans-  haS    glVCU    nSC    tO    UlUCh    dlf- 

yerse     section     in     the     region     of     n.     /,  fej-gj^^^       ^f       OpiuioU.          The 

longitudinal    fibrillse;     n,    Krause  s    mem-  ^ 

brane;    nl,    nucleus;    r,    radial    fibrills;    3,  moSt     plaUSiblc     vicW     is     that 

sarcolemma. — After    Janet.  ,                       r^    :         i  ^                t          i. 

of  van  Ciehuchten,  Janet 
and  others,  who  hold  that  both  kinds  of  dark  bands  (  h'ig 
no)  consist  of  highly  elastic  threads  of  spongioplasni  (aniso- 
tropic)   embedded  in  a  matrix  of  clear,  semi-fluid,  nutritive 


Fig.  no. 


ENTOMOLOGY 


hyaloplasm  (isotropic).  The  spongioplasmic  threads  of  the 
long-  bands  extend  longitudinally  and  those  of  the  short  bands 
{"  Krause's  membrane")  radially,  in  respect  to  the  form  of 
the  fiber.  Moreover,  the  attenuated  extremities  of  the  longi- 
tudinal fibrillse  connect  with  the  radial  fibrillje,  the  points  of 
connection  being  marked  by  slight  thickenings,  or  nodes, 
which  go  to  make  up  Krause's  membrane. 

Under  nervous  stimulus  a  muscle  shortens  and  thickens 
because  its  component  fibers  do,  and  this  in  turn  is  attributed 
to  the  shortening  and  thickening  of  the  longitudinal  fibrillje. 
When  the  stimulus  ceases,  the  radial  fibrillse,  by  their  elas- 
ticity, possibly  pull  the  longitudinal  ones  back  into  place.  The 
last  word  has  not  been  said,  however,  upon  this  perplexing 
subject. 

Muscular  Power. — The  muscular  exploits  of  insects  appear 
to  be  marvellous  beside  those  of  larger  animals,  though  they 
are  often  exaggerated  in  popular  writings.  The  weakest  in- 
sects, according  to  Plateau,  can  pull  five  times  their  own 
weight  and  the  average  insect,  over  twenty  times  its  weight, 
while  Donacia  (Chrysomelidje)  can  pull  42.7  times  its  weight. 
As  contrasted  with  these  feats,  a  man  can  pull  in  the  same 
fashion  but  .86  of  his  weight  and  a  horse  from  .5  to  .83.  How 
are  these  dififerences  explained? 

It  is  incorrect  to  say  that  the  muscles  of  insects  are  stronger 
than  those  of  vertebrates,  for,  as  a  matter  of  fact,  the  contrac- 
tile force  of  a  vertebrate  muscle  is  greater  than  that  of  an 
insect  muscle,  other  things  being  equal.  The  apparently 
greater  strength  of  an  insect  in  proportion  to  its  weight  is 
accounted  for  in  several  ways.  The  specific  gravity  of  chitih 
is  less  than  that  of  bone,  though  it  varies  greatly  in  both  sub- 
stances. Furthermore,  the  external  skeleton  permits  muscu- 
lar attachments  of  the  most  advantageous  kind  as  compared 
with  the  internal  skeleton,  so  that  the  muscles  of  insects  sur- 
pass those  of  vertebrates  as  regards  leverage.  These  reasons 
are  only  of  minor  importance,  however.  Small  animals  in 
general  appear  to  be  stronger  than  larger  animals   (allowing 


ANATOMY    AND    PHYSIOLOGY  89 

for  the  differences  in  weis^-lit)  for  tlie  same  reason  tliat  a 
smaller  insect  has  more  conspicnons  streni^th  than  a  larger 
one,  when  the  two  are  similar  in  everything  except  weight. 
\'i)v  example:  where  a  bumble  bee  can  pull  16.1  times  its  own 
weight,  a  honey  bee  can  pull  20.2 ;  and  where  the  same  bumble 
bee  can  carry  wdiile  flying  a  load  0.63  of  its  own  weight,  the 
honey  bee  can  carry  0.78.  Always,  as  Plateau  has  shown,  the 
lighter  of  two  insects  is  the  stronger  in  respect  to  external 
manifestations  of  muscular  force — in  the  ratio  of  this  muscu- 
lar strength  to  its  own  weight. 

To  understand  this,  let  us  assume  that  a  beetle  continues  to 
grow  (as  never  happens,  of  course).  As  its  weight  is  increas- 
ing so  is  its  strength — but  not  in  the  same  proportion.  For 
while  the  weight — say  that  of  a  muscle — increases  as  the  cube 
of  a  single  dimension,  the  strength  of  the  muscle  (depending 
solely  upon  the  area  of  its  cross  section)  is  increasing  only  as 
the  square  of  one  dimension — its  diameter.  Therefore  the 
increase  in  strength  lags  behind  that  of  weight  more  and 
more;  consequently  more  and  more  strength  is  required  sim- 
ply to  move  the  insect  itself,  and  less  and  less  surplus  strength 
remains  for  carrying  additional  weight.  Thus  the  larger  in- 
sect is  apparently  the  weaker,  though  it  is  actually  the 
stronger,  in  that  its  total  muscular  force  is  greater. 

The  writer  uses  this  explanation  to  account  also  for  the 
inability  of  certain  large  beetles  and  other  insects  to  use  their 
wings,  though  these  organs  are  well  developed.  Increasing 
w^eight  (due  to  a  larger  supply  of  reserve  food  accumulated 
bv  the  larva)  has  made  such  demands  upon  the  muscular 
power  that  insufficient  strength  remains  for  the  purpose  of 
flight. 

Statements  such  as  this  are  often  seen — a  flea  can  jump  a 
meter,  or  six  hundred  times  its  own  length.  Almost  needless 
to  say,  the  length  of  the  body  is  no  criterion  of  the  muscular 
power  of  an  animal. 

4.  Nervous  System 
The  central  nerx'ous  system  extends  along  the  median  line 
of  the  floor  of  the  body  as  a  series  of  ganglia  connected  by 


90 


ENTOMOLOGY 


b-W 


nerve  cords.     Typically,  there  is  a  gan- 
glion (double  in  origin)  for  each  primary 

qI       segment,    and   the    connecting   cords,    or 

,  coiiuiiissiircs,  are  paired;  these  conditions 

are  most  nearly  realized  in  embryos  and 

I  in  the  most  generalized  insects — Thysa- 

"'^^  nura  (  Fig.  1 1 1  ) .  In  all  adult  insects, 
however,  the  originally  separate  ganglia 
consolidate  more  or  less  (Fig.   112)  and 

r  the     commissures     frequently     unite     to 

form    single    cords.     Thus    in    Tabainis 

^^  (  1' ig-  II-.  C)  the  three  thoracic  gan- 
glia   have    united    into    a    single    com- 

flf  poi^^i'it^l  ganglion  and  the  abc^ominal  gan- 
glia are  concentrated  in  the  anterior 
part  of  the  abdomen ;  in  the  grasshop- 
per, the  ner\-e  cord,  double  in  the  tho- 
rax, is  single  in  the  abdomen.  Various 
other  modifications  of  the  same  nature 
occur. 

Cephalic  Ganglia. — In  the  head  the 
primitive  ganglia  always  unite  to  form 
two  compound  ganglia,  namely  the 
brain  and  the  subccsophagcal  ganglion 
( disregarding  a  few  anomalous  cases 
in  which  the  latter  is  said  to  be 
absent). 

The  brain,  or  suprao'sophagcal  gan- 
glion (Fig.  113),  is  formed  by  the  union 
of  three  primitive  ganglia,  or  ncurouicrcs 

0  (Fig.    55),    namely,    (T)    the   protoccrc- 

bruni,  which  gives  off  the  pair  of  optic 
nerves;    (2)    the    dcntoccrcbnini,    which 

Central     nervous     system 

of   a  thysanuran,   Machilis.  nerve;    b,    brain;    c,    compound    eye;    /,    labial    nerve;    m, 

The    thoracic    and    abdom-  mandibular    nerve;    mx,    maxillary    nerve;    o,    cesophagus; 

inal    ganglia   are   numbered  ol,  optic  lobe;   s,  suboesophageal  ganglion;   sy,   sympathetic 

in    succession,     a,   antennal  nerve.— After  Oudemans. 


ANATOMY    AND    PHYSIOLOGY 


91 


innervates  the  antenn:c;  and  (3)  the  Irilocmivuin ,  which  in 
Apterygota  hears  a  pair  of  ni(hmentar_\'  a])pen(la<;es  that  are 
reg-arded  as  traces  of  a  second  i)air  of  antenna\ 


Successive   stages  in   the  concentration   of   tlie   central   nervous   system   of   Diptera.     A, 
Cliirowiniis ;  B,  Enipis;  C,   Tabmiiis;  D,  Sarcophaga. — After  Br,\ndt. 

Fk;.   113. 


Nervous  system  of  the  head  of  a  cockroach,  a,  antennal  nerve;  ag,  anterior  lateral' 
ganglion  of  sympathetic  system;  b,  brain;  d,  salivary  duct;  /,  frontal  ganglion;  h,  hypo- 
pharynx;  /,  labrum;  ii,  labium;  m,  mandibular  nerve;  mx,  maxillary  nerve;  n!,  nerve  to 
labrum;  >i/t,  nerve  to  labium;  o,  optic  nerve;  of,  oesophageal  commissure;  o<?,  CBsophagus; 
pg,  posterior  lateral  ganglion  of  sympathetic  system;  r,  recurrent  nerve  of  sympa- 
thetic system;    s,   suboesophageal   ganglion. — After   Hofer. 


The   suboesophageal   ganghon    (Fig.    113)    is   ahvays   con- 
nected with  the  brain  l)y  a  pair  of  nerve  cords   {wsopliagcal 


92 


ENTOMOLOGY 


coiiunissurcs)    between    which   the   fESophagus   passes.     This 

compound  ganglion  represents  at  most  four  neuromeres :   ( i ) 

mandihnlav,    innervating    the    mandibles;     (2)    snpcvUngual, 

found  by  the  author  in   Collembola, 

l-IG.    114. 

but  not  yet  reported  in  the  less  gen- 
eralized insects;  (3)  maxillary,  inner- 
^^^_^^  vating  the  maxilke  ;  (4)  labial,  which 

<:5nj(     Y   yi^  sends  a  pair  of  nerves  to  the  labium. 

^~-J  -^"^^^■"^'^    Ur,  The  minute  structure  of  the  brain, 

though  highly  complex,  has  received 
considerable  study,  but  will  not  be 
described  here  for  the  reason  that  the 
anatomical  facts  are  of  no  general 
interest  so  long  as  their  physiological 
interpretation  remains  obscure. 

Sympathetic  System.  — ^  L  y  i  n  g 
along  the  median  dorsal  line  of  the 
oesophagus  is  a  recurrent,  or  stoma  to- 
gastric,  nerve  (Fig.  114),  which 
arises  anteriorly  in  a  frontal  gan- 
glion and  terminates  posteriorly  in 
a  stomachic  ganglion  situated  at 
the  anterior  end  of  the  mid  intes- 
tine. Connected  with  the  recurrent 
nerve  are  two  pairs  of  lateral  ganglia, 
the  anterior  of  which  innervate  the 
dorsal  vessel  and  the  posterior,  the 
tracheae  of  the  head.  The  ^'entral 
nerve  cord  may  include  also  a  median 
nerve  thread  (Fig.  11 1)  which  gives 
off  paired  transverse  nerves  to  the 
muscles  of  the  spiracles. 
Structure  of  Ganglia  and  Nerves. — A  ganglion  consists 
of  (i)  a  dense  cortex,  composed  of  ganglion  cells  (Fig.  115), 
each  of  which  has  a  large  rounded  nucleus  and  gives  off  usu- 
ally a  single  nerve  fiber;  and   (2)   a  clear  medullary  portion 


Sympathetic  nervous  system 
of  an  insect,  diagrammatically 
represented.  a,  antenna! 
nerve;  b,  brain;  f,  frontal 
ganglion;  /,  /,  paired  lateral 
ganglia;  m,  nerves  to  upper 
mouth  parts;  o,  optic  nerve; 
r,  recurrent  nerve;  s,  nerve  to 
salivary  glands;  st,  stomachic 
ganglion. — After   Kolbe. 


ANATOMY    AND    PHYSIOLOGY 


93 


(Piiiiktsubsfaii::;)  derived  from  the  processes  of  the  cortical 
ganghon  ceHs  and  serving  as  the  place  of  origin  of  nerve  fihril- 
lae.  There  are,  however,  ganglion  cells  from  which  processes 
may  pass  directly  into  nerve  fibrilhc. 

A  ncr\c,  in  an  insect,  consists  of  an  a.vis-cyltiidcr,  composed 
of  hhrilla-,  and  an  enveloping  membrane,  or  uriirilriniiia.  The 
axis-c\lin(ler  is  the  transmitlinsj"  i)ortion  and  the  ij'.'nii'iia  are 


Fig. 


Transverse    section    of    an    abdominal    ganglion    of    a    caterpillar,     a,    axis-cylinder;    g, 
ganglion   cells;    n,   nenrilennna;   p,    Punktsubstanz. 

the  trophic  centers,  i.  e.,  they  regulate  nutrition.  A  nerve  is 
always  either  sensory,  transmitting  impulses  inward  from  a 
sense  organ;  or  else  motor,  conveying-  stimuli  from  the  central 
nervous  system  outward  to  muscles,  glands,  or  other  organs. 

Functions. — The  brain  innervates  the  chief  sensory  organs 
(eyes  and  antennae)  and  converts  the  sensory  stimuli  that  it 
receives  into  motor  stimuli,  which  effect  co-ordinated  muscular 
or  other  movements  in  response  to  particular  sensations  from 
the  en\'ironment.  The  brain  is  the  seat  of  the  will,  using  the 
term  "  will  "  in  a  loose  sense;  it  directs  locomotor  mo^'ements 
of  the  legs  and  wings.  An  insect  deprived  of  its  brain  cannot 
go  to  its  food,  though  it  is  able  to  eat  if  food  be  placed  in  con- 
tact with  the  end-organs  of  taste,  as  those  of  the  palpi ;  further- 
more, it  walks  or  flies  in  an  erratic  manner,  indicating  a  lack 
of  co-ordination  of  nuiscular  action. 

The  suboesophageal  ganglion  controls  the  mouth  parts,  co- 
ordinating their  movements  as  well  as  some  of  the  bodily 
movements. 


94  ENTOMOLOGY 

The  thoracic  gangHa  govern  the  appendages  of  their  respec- 
tive segments.  These  gangha  and  those  of  the  abdomen  are 
to  a  great  extent  independent  of  brain  control,  each  of  these 
gangha  being  an  individual  motor  center  for  its  particular 
segment.  Thus  decapitated  insects  are  still  able  to  breathe, 
walk  or  fly,  and  often  retain  for  several  days  some  power  of 
movement. 

In  regard  to  the  sympathetic  system,  it  has  been  shown  ex- 
perimentally that  the  frontal  ganglion  controls  the  swallowing 
mo\'ements  and  exerts  through  the  stomatogastric  nerve  a 
regulative  action  upon  digestion.  The  dorsal  sympathetic  sys- 
tem controls  the  dorsal  vessel  and  the  salivary  glands,  while 
the  ventral  sympathetic  system  is  concerned  with  the  spiracu- 
lar  muscles. 

5.  Sense  Organs 

For  the  reception  of  sensory  impressions  from  the  external 
world,  the  armor-like  intesrument  of  insects  is  modified  in  a 


another  may  occur  on  almost  any  part  of  an  insect,  they  are 
most  numerous  and  varied  upon  the  head  and  its  appendages, 
particularly  the  antennae. 

Antennal  Sensilla. — Some  idea  of  the  diversity  of  form 
in  antennal  sense  organs  may  be  obtained  from  Figs.  1 16-125, 
taken  from  a  recent  paper  by  Schenk.  whose  useful  classifica- 
tion of  antennal  scusilla,  or  sense  organs,  is  here  outlined : 

1.  Scusilluin  caloconicuin — a  conical  or  peg-like  projection 
immersed  in  a  pit  (Figs.  116-117).  In  all  probability 
olfactory. 

2.  ^.  hasiconicuin — a  cone  projecting  above  the  general  sur- 
face (Fig.  118).     Probably  olfactory. 

3.  5^.  styloconicum — a  terminal  tooth  or  peg  seated  upon  a 
more  or  less  conical  base  (Fig.  119).     Olfactory. 

4.  6^.  cliccticuni — a  bristle-like  sense  organ  (Fig.  120). 
Tactile. 

5.  6^.  tvichodcum — a  hair-like  sense  organ  (Figs.  121,  122). 
Tactile. 


ANATOMY    AND    PHYSIOLOGY 


95 


6.  5.    placodcuni — a   membranous   plate,    its   outer   siu'face 
continuous  with  the  g-eneral  integument    (  h'ig.    123).      h\inc- 

FiGs.  1 16-125. 


Types  of  antennal  sensilla,  in  longitudinal  section  (excepting  Figs.  119  and  120). 
Fig.  116,  sensillum  cotloconicum;  117,  cceloconicum;  118,  basiconicum;  119,  stylo- 
conicum;  120,  chseticum;  121,  trichodeum;  122,  trichodeum;  123,  placodeum;  124, 
ampullaceum;  125,  ampullaceum;  c,  cuticula;  h,  hypodermis;  n,  nerve;  s,  sensory  cell. 
Figs.  116,  118,  121,  123,  124,  honey  bee,  Apis  mellifera;  117,  119,  122,  moth,  FiJonia 
piniaria;    120,   moth,   Ino  pruni;   125,   wasp,    Vespa   crabro. — After   Schenk. 


96  ENTOMOLOGY 

tion  doubtful ;  not  auditory  and  probably  not  olfactory,  though 
the  function  is  doubtless  a  mechanical  one;  Schenk  suggests 
that  they  are  affected  by  air  pressure,  as  when  a  bee  or  wasp 
is  moving  about  in  a  confined  space. 

7.  5.  ampiiUaccnm — a  more  or  less  flask-shaped  cavity  with 
an  axial  rod  (Figs.  124,  125).      Probably  auditory. 

These  types  of  sensilla  will  be  referred  to  in  physiological 
order. 

Touch. — The  tactile  sense  is  highly  developed  in  insects, 
and  end-organs  of  touch,  unlike  those  of  other  senses,  are  com- 
monly distributed  over  the  entire  integument,  though  the  an- 
tenucC,  palpi  and  cerci  are  especially  sensitive  to  tactile  impres- 
sions. 

The  end-organs  of  touch  are  bristles  (sensilla  ch^etica)  or 
hairs  (sensilla  trichodea),  each  arising  from  a  special  hypo- 
dermis  cell  and  having  connection  with  a  nerve.  Sensilla 
ch?etica  doubtless  receive  impressions  from  foreign  bodies, 
while  sensilla  trichodea,  being  best  developed  in  the  swiftest 
flying  insects  and  least  so  in  the  sedentary  forms,  may  be 
affected  by  the  resistance  of  the  air,  when  the  insect  or  the  air 
itself  is  in  motion. 

Not  all  the  hairs  of  an  insect  are  sensory,  however,  for  many 
of  them  have  no  nerve  connections. 

In  blind  cave  insects  the  antennre  are  very  long  and  are  ex- 
quisitely sensitive  to  tactile  impressions. 

Taste. — The  gustatory  sense  is  unquestionably  present  in 
insects,  as  is  shown  both  by  common  observation  and  by  pre- 
cise experimentation.  \\\\\  fed  wasps  with  sugar  and  then 
replaced  it  with  powdered  alum,  which  the  wasps  unsuspect- 
ingly tried  but  soon  rejected,  cleaning  the  tongue  with  the 
fore  feet  in  a  comical  manner  and  manifesting  other  signs  of 
what  we  may  call  disgust.  Forel  offered  ants  honey  mixed 
with  morphine  or  strychnine;  the  ants  began  to  feed  but  at 
once  rejected  the  mixture.  In  its  range,  however,  the  gusta- 
tory sense  of  insects  differs  often  from  that  of  man.  Thus 
\\\\\  found  that   Hymenoptera  refused  honey  with  which  a 


ANATOMY    AND    PHYSIOLOGY 


97 


very  little  glycerine  had  been  mixed  (thoug-h  Muscidrc  did  not 
object  to  the  glycerine)  and  Forel  found  that  ants  ate  iinsus- 


Section  through  tongue  of  wasp,  I'cspa  ml 
hypodermis;  n,  nerve;  ob,  gustatory  bristle;  pli 
tactile  bristle.— After  Will. 


'i^.     c,    ciiticula 
rotecting   hair; 


gland    cell;    li, 
sensory   cell;    tb, 


Fig.  i; 


pectingiy  a  mixture  of  honey  and  phosphorus  until  some  of 
them  were  killed  by  it.  Under  the  same  circumstances,  man 
would  be  able  to  detect  the  phosphorus 
but  not  the  glycerine. 

Location  of  Gustatory  Organs. — As 
would  be  expected,  the  end-organs  of 
taste  are  situated  near  the  mouth,  com- 
monly on  the  hypopharynx  (Fig.  126), 
epipharynx  and  maxillary  palpi.  On  the 
tongue  of  the  honey  bee  the  taste  organs 
appear  externally  as  short  setse  (Fig. 
127)  and  on  the  maxillae  of  a  wasp  as 
pits,  each  with  a  cone,  or  peg,  projecting 
from  its  base  (Figs.  128,  129).  Similar 
taste  pits  and  pegs  have  been  found  by 
Packard  on  the  epipharynx  in  most  of  the 
mandibulate  orders  of  insects. 
Histology- — The  end-organs  of  taste  arise  from  special 
hypodermis  cells,  as  minute  setae  or,  more  commonly,  pegs. 


Tongue  of  honey  bee, 
Apis  mellifera.  p,  pro- 
tecting bristles;  s,  ter- 
minal spoon;  t,  taste 
setae. — After    Will. 


98 


ENTOMOLOGY 


Fig.  128. 


..-tc 


—tk 


each  seated  in  a  pit,  or  cup,  and  connected  with  a  nerve  fiber 
(Figs.   129,  130).     In  some  cases,  however,  it  is  difficult  to 

decide  whether  a  given  organ 
is  gustatory  or  olfactory,  owing 
to  the  similarity  between  these 
two  kinds  of  structures.  In 
aquatic  insects,  indeed,  the 
senses  of  taste  and  smell  are  not 
differentiated,  these  forms  hav- 
ing with  other  of  the  lower 
animals  simply  a  "  chemical  " 
sense. 

Smell. — In  most  insects  the 
sense  of  smell  is  highly  efficient 
and  in  many  species  it  is  incon- 
ceivably acute.  Hosts  of  in- 
sects depend  chiefly  on  their 
olfactory  powers  to  find  food, 
for  example  many  beetles,  the 
flesh   flies   and   the  flower-visit- 


Under     side     of     left     maxilla  of 

wasp,    Vespa  zndgaris.     p,   palpus;  pr, 

protecting    hairs;     tc,    taste    cup;  th, 
tactile  hair. — After  Will. 


the  opposite   sex,   as   is  notably 
the    case    in    saturniid    moths. 


In  dragon  flies,  however,  this 
sense  is  relied  upon  far  less 
than  that  of  sight. 

Organs  of  Smell.  —  By 
means  of  simple  but  conclu- 
sive experiments,  Hauser  and 
others  have  shown  that  the 
antennae  are  frequently  olfac- 
tory— though  not  to  the  ex- 
clusion of  tactile  or  auditory 
functions,  of  course.  Hauser 
found  that  ants,  wasps,  vari- 
ous flies,  moths,  beetles  and 
larvse,   which    react   violently   toward    the   vapor   of   turpen- 


Longitudinal  section  of  gustatory 
end-organ  {tc,  of  Fig.  128).  c,  cutic- 
ula;  h,  hypodermis;  sc,  sensory  cell; 
tc,  taste  cup. — After  Will. 


ANATOMY    AND    PHYSIOLOGY 


99 


tine,  acetic  acid  and  other  pnngent  fluids,  no  longer  re- 
spond to  the  same  stimuli  after  their  antenna'  have  been 
amputated  or  else  covered  with  paraftine  to  exclude  the 
air.  His  experiments  were  conducted  under  conditions 
such    that    the    results    could    not   be    ascribed    to    the    shock 


Fir;.   T30. 


Taste     cup 

from     maxilla 

of       Bombus. 

sc,       sensory 

cell;   n,  nerve. 

—After  Will. 

Section  of  antennal  olfac- 
tory organ  of  grasshopper, 
Caloptcniis.  c,  cuticula;  m, 
membrane;  n,  nucleus  of 
sensory  cell;  nv,  nerve;  p, 
pit  with  olfactory  peg;  pg, 
pigment. — After   Hauser. 


of  the  operation  or  to  effects  upon  the  gustatory  or  res- 
piratory systems ;  except  for  having  lost  the  sense  of  smell, 
the  insects  experimented  upon  behaved  in  a  normal  manner.  It 
should  be  said,  however,  that  Carahus,  Mclolontlia  and  Silpha 
still  reacted  to  some  extent  toward  strong  vapors  even  after  the 
extirpation  of  the  antennae ;  while  in  Hemiptera  the  loss  of  the 
antennas  did  not  lessen  the  response  to  the  odors  used.  These 
facts  indicate  that  the  sense  of  smell  is  not  always  confined  to 
the  antennae ;  indeed  the  maxillary  palpi  are  frequently  olfac- 
tory, as  in  Silpha  and  Hydoticus;  also  the  cerci,  as  in  the  cock- 
roach and  other  Orthoptera.     Experiments   indicate  that  an 


lOO 


ENTOMOLOGY 


insect  perceives 

Fig.  132. 


Section  through  antennal  olfactory 
pit  of  fly,  Tabaiius.  c,  cuticula;  p, 
pit  with  peg;  pb,  protecting  bristles; 
s,  sensory  cell. — After  H.'iUSEr. 


some  odors  by  means  of  the  antenna  and 
others  by  the  palpi  or  other 
organs.  Hauser  found  that 
the  flies  Sarcophaga  and  Cal- 
liphora,  after  the  amputation 
of  their  antennae,  became 
quite  indifferent  toward  de- 
cayed meat,  to  which  they 
had  previously  swarmed  with 
great  persistence,  though 
their  actions  in  all  other  re- 
spects remained  normal. 
]\Iales  of  many  moths  and  a 
few  beetles  are  unable  to  find 


Fig.  133- 


cn 


the  females  (see  beyond)  when  the  for- 
mer are  deprived  of  the  use  of  their 
antennae. 

End-Organs. — Structures  which  are 
regarded  as  olfactory  end-organs  occur 
commonly  on  the  antennje.  often  on  the 
maxillary  and  labial  palpi  and  sometimes 
on  the  cerci.  These  end-organs  are  hy- 
podermal  in  origin  and  consist,  generally 
speaking,  of  a  multinucleate  cell  (Fig. 
131)  penetrated  by  a  nerve  and  prolonged 
into  a  chitinous  bristle  or  peg,  which  is 
more  or  less  enclosed  in  a  pit,  as  in  Ta- 
baniis  (Fig.  132).  In  many  instances, 
however,  the  end-organs  take  the  form  of 
teeth  or  cones  projecting  from  the  gen- 
eral surface  of  the  antenna,  as  in  J^cspa 
(Fig.  133).  These  cones  are  usually  less 
numerous  than  the  pits;  in  J\^spa  crabro, 
for  example,  the  teeth  number  700  and 
the  pits  from  13.000  to  14.000  on  each 
antenna.     The  pits  are  even  more  numerous  in  some  other 


Longitudinal  section 
of  antennal  olfactory 
organ  of  wasp,  Vespa. 
c,  olfactory  cell;  cn,  ol- 
factory cone;  ct,  cutic- 
ula; h,  hypodermis  cells; 
n,  nerve;  r,  rod. — After 
Hauser. 


ANATOMY    AND    PHYSIOLOGY 


insects ;  tlins  there  are  as 
many  as  17.000  on  each  an- 
tenna of  a  l)l<)\v  fly  (Hicks). 
The  male  of  Mclolontha  vul- 
garis, which  seeks  ont  the 
female  hy  the  sense  of  smell, 
has  according-  to  Hauser  39,- 
000  pits  on  each  antenna,  and 


Fig.  134. 


the  female  onl\-  :5s. 000. 


Pit^ 


presumahly  olfactory  in  fnnc- 
tion  ha\e  l)een  fonnd  hy 
Packard  on  the  maxillary  and 
lahial  palpi  of  Pcrla  and  on 
the  cerci  of  the  cockroach 
Pcriplancta  aincvicana.     Vom 


Longitudinal    section    of    a    portion    of    a 

caudal     appendage     of     a     cricket,     Grylliis 

domesticus.     b,    bladder-like    hair;    c,    cutic- 

ula;     /;,     hypodermis;     n,    nerve;     ns,     non- 

Rath  has  deSCrihed    four  kinds     sensory    sets;    sc,    sense    cell;    sh,    sensory 


hair 


.\fter  voM   Rath. 


Fi'--   135- 


of  sense  hairs   from  the  two 

larger  of  the  four  caudal  appen- 
dages of  a  cricket.  Gryllus;  some 
of  these  (Fig.  134)  may  be  olfac- 
tory, though  possibly  tactile.  The 
same  author  found  on  the  terminal 
palpal  segment  in  various  Lepidop- 
tera  a  large  flask-shaped  invagina- 
tion (Fig.  135)  into  wdiich  pro- 
ject numerous  chitinous  rods,  each 
a  process  of  a  sensory  cell,  which 
is  supplied  by  a  branch  of  the  prin- 
cipal palpal  nerve ;  these  peculiar 
organs  are  inferred  to  be  olfactory. 
The  chief  reason  for  regard- 
ing these  various  end-organs  as 
olfactory  is  that  they  appear 
Longitudinal  section  of  ape.x  of    ^^om   their   structurc   to   he   better 

palpus  of  Pieris.    c,  cuticuia;   h,    adapted    to    rcccivc    that    kind    of 

hypodermis;     n,     nerve;     s,     scales;  ... 

sc,  sense  ceiis.-After  vom  Rath,      ^i"  impressioii  than  any  Other,   SO 


I02  ENTOMOLOGY 

far  as  we  can  judge  from  our  own  experience.  Though  it  is 
easy  to  demonstrate  that  the  antennae,  for  example,  are  olfac- 
tory, it  frequently  happens  that  the  antennae  bear  several  dis- 
tinct forms  of  sensory  end-organs,  so  minute  and  intermingled 
that  their  physiological  differences  can  scarcely  be  ascertained 
by  experiment  but  must  be  inferred  from  their  peculiarities  of 
structure.  Schenk,  however,  has  arrived  at  precise  results 
by  comparing  the  antennal  sensilla  in  the  two  sexes,  selecting 
species  in  which  the  antennae  exhibit  a  pronounced  sexual 
dimorphism,  in  correlation  with  sexual  differences  of  behavior. 
Taking  NotolopJius  (Orgyia)  antiqua,  in  which  the  male  seeks 
out  the  female  by  means  of  antennal  organs  of  smell,  he  finds 
that  the  male  has  on  each  antenna  about  600  sensilla  coelo- 
conica  and  the  female  only  75  ;  similarly  in  the  geometrid  Fido- 
7iia,  in  which  the  ratio  is  350  to  100.  The  sensilla  styloconica, 
also,  of  these  two  genera  are  regarded  as  olfactory  organs. 
These  two  kinds  of  end-organs  are  not  only  structurally  adapted 
for  the  reception  of  olfactory  stimuli,  but  their  numerical  dif- 
ferences accord  with  the  observed  differences  in  the  olfactory 
powers  of  the  two  sexes,  there  being  no  other  antennal  end- 
organs  to  enter  into  the  consideration. 

Assembling. — It  is  a  fact,  well  known  to  entomologists, 
that  the  females  of  many  moths  and  some  beetles  are  able  by 
exhaling  an  odor  to  attract  the  opposite  sex,  often  in  consid- 
erable numbers.  Under  favorable  conditions,  a  freshly 
emerged  female  of  the  promcthca  moth,  exposed  out  of  doors 
in  the  latter  part  of  the  afternoon,  will  attract  scores  of  the 
males.  A  breeze  is  essential  and  the  males  come  up  against 
the  wind;  if  they  pass  the  female,  they  turn  back  and  try  again 
until  she  is  located,  vibrating  the  antennae  rapidly  as  they  near 
her.  The  female,  meanwhile,  exhales  an  appreciable  odor, 
chiefly  from  the  region  of  the  ovipositor,  and  males  will  con- 
gregate on  the  ground  at  a  spot  where  a  female  has  been.  If 
one  of  these  males  is  deprived  of  the  use  of  his  antennae,  how- 
ever, he  flutters  about  in  an  aimless  way  and  is  no  longer  able 
to  find  the  female. 


ANATOMY    AND    PHYSIOLOGY  IO3 

Among-  beetles,  males  of  Polyphylla  gather  and  scratch  at 
places  where  females  are  about  to  emerge  from  the  ground. 
Prionus  also  assembles,  as  Mrs.  Dimmock  observed  in  Massa- 
chusetts. In  this  instance  many  males,  with  palpitating  an- 
tennae, ran  and  flew  to  the  female;  moreover,  a  number  of 
females  were  attracted  to  the  scene. 

Sounds  of  Insects. — Before  considering  the  sense  of  hear- 
ing, some  account  of  the  sounds  of  insects  is  desirable.  Most 
of  these  are  made  by  the  vibrations  of  a  membrane  or  by  the 
friction  of  one  part  against  another. 

The  wings  of  many  Diptera  and  Hymenoptera  vibrate  with 
sufficient  speed  and  regularity  to  give  a  definite  note.  The 
wing  tone  of  a  honey  bee  is  A'  and  that  of  a  common  house 
fly  is  F'.  From  the  pitch  the  number  of  vibrations  may  be 
determined;  thus  A'  means  440^  vibrations  per  second  and 
F',  352.  The  numbers  thus  ascertained  may  be  verified  by 
Marey's  graphic  method  (Fig.  74)  ;  he  found  that  the  fly 
referred  to  actually  made  330  strokes  per  second  against  the 
smoked  surface  of  a  revolving  cylinder. 

Flies,  bees,  dragon  flies  and  some  beetles  make  buzzing  or 
humming  sounds  by  means  of  the  spiracles,  there  being  behind 
each  spiracle  a  membrane  or  chitinous  projection  wdiich  vi- 
brates during  respiration.  This  "  voice  "  should  be  distin- 
guished from  the  wing  tone  when  both  are  present,  as  in  bees 
and  flies.  A  fly  will  buzz  when  held  by  the  wings,  and  some 
gnats  continue  to  buzz  aft'er  losing  wings,  legs  and  head. 
The  wing  tone  is  the  more  constant  of  the  two ;  in  the  honey 
])ee  it  is  A',  falling  to  E'  if  the  insect  is  tired,  while  the  spirac- 
ular  tone  of  the  same  insect  is  at  least  an  octave  higher  (A") 
and  often  rises  to  B"  or  C" ,  according  to  the  state  of  the  ner- 
vous system ;  in  fact,  it  is  possible  and  even  probable  that  vari- 
ous spiracular  tones  express  different  emotions,  as  is  indicated 
by  the  effects  produced  by  the  voice  of  the  old  queen  bee  upon 
the  young  queens  and  the  males. 

'  Upon  tlie  basis  of  C  as  264  vibrations  per  second.  The  C  of  the 
physicist  has  256  as  its  frequency  of  vibration. 


I04  .  ENTOMOLOGY 

The  well-known  "  shrilling  "  of  the  male  cicada  is  produced 
by  the  rapid  vibration  of  a  pair  of  membranes,  or  drums,  sit- 
uated on  the  basal  abdominal  segment,  and  vibrated  each  by- 
means  of  a  special  muscle. 

Frictional  sounds  are  made  by  beetles  in  a  great  variety  of 
ways :  by  the  rubbing  of  the  pronotum  against  the  mesonotum 
(many  Cerambycidse)  ;  or  of  abdominal  ridges  against  elytral 
rasps  {Elaphrns,  Cychnis)  ;  or  two  dorsal  abdominal  rasps 
against  specialized  portions  of  the  wing  folds  (Passahis  cor- 
nutus) ,  not  to  mention  other  methods.  In  most  cases  one 
part  forms  a  rasp  and  the  other  a  scraper,  for  the  production 
of  sound. 

In  many  of  these  instances  the  sound  serves  to  bring  the 
two  sexes  together  and  is  not  necessarily  confined  to  one  sex; 
thus,  in  Passahis  corn  lit  us  both  sexes  stridulate. 

A  few  moths  (Sphingidse)  and  a  few  butterflies  make 
sounds ;  the  South  American  butterfly  Agcronia  feronia  emits 
a  sharp  crackling  noise  as  it  flies.  A  rasp  and  a  scraper  have 
been  found  in  several  ants,  though  ants  very  seldom  make  any 
sounds  that  can  be  distinguished  by  the  human  ear;  Mutilla, 
however,  makes  a  distinct  squeaking  sound  by  means  of  a 
stridulating  organ  similar  to  those  of  ants. 

Stridulating  organs  attain  their  best  development  in  Orthop- 
tera,  in  which  group  the  ability  to  stridulate  is  often  restricted 
to  the  male,  though  not  so  often  as  is  commonly  supposed. 
Among  Acridiidse,  Stenobotliriis  rubs  the  hind  femora  against 
the  tegmina  to  make  a  sound,  the  femur  bearing  a  series  of 
teeth,  which  scrape  across  the  elevated  veins  of  the  wing-cover; 
while  the  male  of  Dissosteira  makes  a  crackling  sound  during 
flight  or  while  poising,  by  means  of  friction  between  the  front 
and  hind  wings,  where  the  two  overlap. 

Locustidae  and  Gryllidse  stridulate  by  rubbing  the  bases  of 
the  tegmina  against  each  other.  Thus  in  the  male  Microcen- 
trum  laurifoliiim  the  left  tegmen,  which  overlaps  the  right, 
bears  a  file-like  organ  of  about  fifty-five  teeth  (Fig.  136),  while 
the  opposite  tegmen  bears  a  scraper,  at  right  angles  to  the  file. 


ANATOMY    AND    PHYSIOLOGY 


105 


The  teg:mina  are  first  spread  a  little:  then,  as  they  close  gTadu- 
ally,  the  scraper  clicks  across  the  teeth,  makino-  from  twenty  to 
thirty  sharp  "  tic  "-like  sounds  in  rapid  succession.  This  call 
guides  the  female  to  the  male  and  when  they  are  a  few  inches 
apart  she  makes  now  and  then  a  short,  soft  chirp,  to  which  he 
responds  Avith  a  similar  chirp,  which  is  quite  unlike  the  first 

Fig.  136. 


Stridulating  organs  of  Microccntrum  laurifolium.  A,  dorsal  aspect  of  file  {st) 
when  the  tegmina  are  closed;  B,  ventral  aspect  of  left  tegmen  to  show  Hie;  C,  dorsal 
aspect  of  right  tegmen  to  show  scraper   (s). 


call  and,  moreover,  is  made  by  the  opening  of  the  tegmina. 
These  and  other  details  of  the  courtship  may  readily  be  ob- 
served in  twilight  and  even  under  artificial  light,  as  the  latter, 
if  not  too  strong,  does  not  disturb  the  pair.  Something  sim- 
ilar may  be  observed  in  the  daytime  in  Orclielimum,  Xiphidiiim 
and  the  tree  crickets,  GEcanthiis.  The  stridulating  areas  are 
usually  membranous  and  the  rasping  organs  are  modified  veins. 


I06  ENTOMOLOGY 

Frequently  the  wing-covers  bulge  out  to  form  a  resonant  cham- 
ber that  reinforces  the  sound. 

The  naturalist  can  recognize  many  a  species  of  grasshopper 
by  its  song;  Scudder  has  expressed  some  of  these  songs  in 
musical  notation.  The  usual  song  of  the  common  meadow- 
grasshopper,  OrclieUniuvi  vulgare,  may  be  represented  by  a 
prolonged  .cr  .  .  .  sound,  followed  by  a  staccato  jip-jip-jip- 
jip.  ... 

In  Orthoptera,  the  frequency  of  stridulation  increases  with 
the  temperature;  and  the  correlation  between  the  two  is  so 
close  that  it  is  easy  to  compute  the  temperature  from  the  num- 
ber of  calls  per  minute,  by  means  of  formulae.  The  formula 
for  a  common  cricket  [probably  a  species  of  Gryllits] ,  as  given 
by  Professor  Dolbear,  is 

^  N-40 

T=  50 -h —  -  -. 
4 

Here  T  stands  for  temperature  and  A^,  the  rate  per  minute. 

A  similar  formula  for  the  katydid  {Cyrtophyllus  perspicil- 

latus),  based  upon  observations  made  by  R.  Hayward,  would 

be 

T=6o-\- -. 

Here,  in  computing  A^,  either  the  "  katy-did  "  or  the  "  she- 
did  "  is  taken  as  a  single  call. 

Hearing. — There  is  no  doubt  that  insects  can  hear.  The 
presence  of  sound-making  organs  is  strong  presumptive  evi- 
dence that  the  sense  of  hearing  is  present.  Female  grass- 
hoppers and  beetles  make  locomotor  and  other  responses  to 
the  sounds  of  the  males,  and  male  grasshoppers  will  answer 
the  counterfeit  chirping  made  with  a  quill  and  a  file. 

Auditory  organs  are  not  restricted  to  any  one  region  of  an 
insect,  but  occur,  according  to  the  species,  on  antennae,  abdo- 
men, legs  or  elsewhere. 

The  antennae  of  some  insects  are  evidently  stimulated  by 
certain  notes,  particularly  those  made  by  their  own  kind. 
Thus   the   antennae   of   the   male   mosquito   are   auditory,    as 


ANATOMY    AND    PHYSIOLOGY 


107 


proved  by  the  well-known  experiments  of  Mayer.  He  fastened 
a  male  Culcx  to  a  microscope  slide  and  sounded  various  tuning 
forks.  Certain  tones  caused  certain  of  the  antennal  hairs  to 
vibrate  sympathetically,  and  the  greatest  amount  of  vibration 
occurred  in  response  to  512  vibrations  per  second,  or  the  note 
C" ,  which  is  approximately  the  note  upon  which  the  female 
hums.  The  male  probably  turns  his  head  until  the  two  an- 
tennae are  equally  affected  l)y  the  note  of  the  female,  when,  by 

Fig.  137. 


S" — d 


Inner  aspect  of  right  tympanal  sense  organ  of  a  grasshopper,  Caloptenus  itallcus. 
b,  chitinous  border;  c,  closing  muscle  of  spiracle;  gn,  ganglion;  m,  tympanum;  n, 
nei-ve;  o,  opening  muscle  of  spiracle;  p,  p,  processes  resting  against  tympanum;  s, 
spiracle;   t)ii,  tensor  muscle  of  tympanum;   z;  vesicle. — After  Gr.^ber. 


going-   Straight   ahead,    he   is   able   to   locate   her   with   great 
precision. 

In  the  lack  of  experimental  evidence,  other  organs  are  in- 
ferred to  be  auditory  on  account  of  their  structure.  Acridiidae 
bear  on  each  side  of  the  first  abdominal  segment  a  tympanal 
sense  organ — the  subject  of  Graber's  well-know^n  figure  (Fig. 
137).  This  organ  is  admirably  adapted  to  receive  and  trans- 
mit sound-waves.  The  tympanum,  or  membrane,  is  tense, 
and  can  vibrate  freely,  as  the  air  pressure  against  the  two  sur- 


io8 


ENTOMOLOGY 


faces  of  the  membrane  is  equalized  by  means  of  an  adjacent 
spiracle,  which  admits  air  to  the  inner  surface.  Resting 
against  the  inner  face  of  the  tympanum  are  two  processes 
(Fig.  137,  />,  p) ,  which  serve  probably  to  transfer  the  vibra- 
tions, and  there  is  also  a  delicate  vesicle  connected  by  means 

of     an     intervening     ganglion 
^^'  ^^  ■  with  the  auditory  nerve,  which 

in  this  case  comes  from  the 
metathoracic  ganglion.  The 
nerve  terminations  consist  of 
delicate  bristle-like  processes 
which  are  probably  affected  by 
the  oscillations  of  the  fluid  con- 
tained in  the  vesicle  just  re- 
ferred to. 

Other  tympanal  organs, 
doubtless  auditory,  are  found 
on  the  fore  tibise  of  Locustid?e, 
ants,  termites  and  Perlidse,  on 
the  femora  of  Pediculid?e  and 
the  tarsi  of  some  Coleoptera. 

Several  types  of  chordotonal 
organs  have  been  described,  of 
which  those  of  the  transparent 
Coretlira  larva  may  serve  as  an 
example.  These  organs,  situ- 
ated on  each  side  of  abdonlinal 
segments  4-10,  inclusive,  con- 
sist each  (Fig.  138)  of  a  tense 
cord,  probably  capable  of  vibra- 
tion, which  is  attached  at  its  posterior  end  to  the  integument 
and  at  its  anterior  end  to  a  ligament.  Between  the  cord  and 
the  supporting  ligament  is  a  small  ganglion,  which  receives  a 
nerve  from  the  principal  ganglion  of  the  segment. 

Vision. — The  external  characters  of  the  two  kinds  of  eyes 
— ocelli   and   compound   eyes — have   already   been   described. 


Chordotonal  sense  organ  of  aquatic 
dipterous  larva,  Coretlira  phimicornis. 
cd,  cord;  eg,  chordotonal  ganglion;  /, 
fibers  of  an  integumental  nerve;  g, 
ganglion  of  ventral  chain;  /,  ligament; 
m,  longitudinal  muscles;  n,  chordotonal 
nerve;  r,  rods  (nerve  terminations);  t, 
tactile   setae. — After   Graber. 


ANATOMY    AND    PHYSIOLOGY 


109 


While  the  lateral  ocelli  are  comparatively  simple  in  structure, 
consisting  of  a  small  number  of  cells,  the  dorsal  ocelli  almost 
rival  the  compound  eyes  in  complexity. 

Dorsal  Ocelli. — These  consist  (Fig.  139)  of  (i)  lens,  (2) 
■rilrcoiis  body,  (3)  retina, 
(4)  nerve  fibers,  (5)  pig- 
mented hypodennis  eells, 
and  (6)  accessory  cells,  be- 
tween the  retinal  cells  and 
the  nerve  fibers.  The  lens, 
usually  biconvex  in  form,  is 
a  local  thickening  of  the 
general  cuticula ;  it  is  sup- 
plemented in  its  function  by 
the  \-itreous  body,  consist- 
ing of  a  layer  of  transpar- 
ent hypodermis  cells;  these 
in  many  insects  are  elon- 
gate, constituting  a  vitreous 
layer  of  rather  more  im- 
portance than  the  one  rep- 
resented in  Fig.  139.  The 
retina  consists  of  cells  more 
or  less  spindle-shaped  and 
associated  in  pairs  or  in  groups  of  two  or  three,  each  group 
being  termed  a  ret  in  it  la.  The  basal  end  of  each  retinal  cell  is 
continuous  with  a  nerve  fiber  (Fig.  140),  according  to  Redi- 
korzew  and  others,  and  in  some  instances  (Calopteryx)  a  nerve 


Median  ocellus  of  honey  bee,  Apis  met- 
lifcra,  in  sagittal  section,  h,  hypodermis; 
/,  lens;  v,  nerve;  p,  iris  pigment;  r,  retinal 
cells;    z;   vitreous   body. — After    Redikorzew. 


or  rhabdoin,  in  the  secretion  of  which  all  the  cells  of  the  retinula 
are  concerned.  Between  the  retinal  cells  and  nerve  fibers  are 
indifferent,  or  accessory  cells.  Pigment  granules,  usually  black, 
are  contained  in  these  cells,  also  in  the  retinal  cells  and  around 
the  lens,  in  the  last  instance  forming  the  iris. 

Vision  by  Ocelli. — Though  the  ocellus  is  constructed  on 


ENTOMOLOGY 


Fig.  140. 


somewhat  the  same  plan  as  the  human  eye,  its  capacity  for 
forming  images  must  l^e  extremely  limited ;  for  since  the  form 
of  the  lens  is  fixed  and  also  the  distance  between  the  lens  and 
the  retina,  there  is  no  power  of  accommo- 
dation, and  most  external  objects  are  out 
of  focus ;  to  make  an  image,  then,  the 
object  must  be  at  one  definite  distance 
from  the  lens,  and  as  the  lens  is  usually 
strongly  convex,  this  distance  must  be 
small ;  in  other  words,  insects,  like  spiders, 
are  very  near-sighted,  so  far  as  the  ocelli 
are  concerned ;  furthermore,  the  small 
number  of  retinal  rods  implies  an  image  of 
only  the  coarsest  kind. 

If  the  compound  eyes  of  a  grasshopper 
are  covered  with  an  opaque  varnish  and 
the  insect  is  placed  in  a  box  with  only  a 
single  opening,  it  readily  finds  its  way  out 
by  means  of  its  ocelli ;  if  all  three  ocelli  are 
also  covered,  however,  it  no  longer  does 
so,  except  by  accident,  though  it  can  make 
its  escape  when  only  one  of  the  ocelli  is 
left  uncovered.  The  ocelli,  then,  can  dis- 
tinguish light  from  darkness — and  they 
are  probably  more  serviceable  to  the  in- 
sect in  this  way  than  in  forming  images. 
Compound  Eyes. — As  regards  deli- 
cacy and  intricacy  of  structure,  the  com- 
pound eye  of  an  insect  is  scarcely  if  at  all 
inferior  to  the  eye  of  a  vertebrate.  In 
radial  section  (Fig.  141),  a  compound  eye 
appears  as  an  aggregation  of  similar 
elongate  elements,  or  ommaiidia,  each  of  which  ends  exter- 
nally in  a  facet.  The  following  structures  compose,  or  are 
concerned  with,  each  ommatidium  :  (i)  cornea,  (2)  crystal- 
line lens,  or  cone,  (3)  rhabdom  and  retinnla,  (4)  pigment  {iris 


■n 

An  ocellar  retinula  of 
the  honey  bee,  composed 
of  two  retinal  cells.  A, 
longitudinal  section ;  B, 
transverse  section ;  ii,  n, 
nerves;  p,  pigment;  r, 
rhabdom.  —  After      Redi- 

KORZEW. 


ANATOMY    AND    PHYSIOLOGY 


I  II 


and  retinal'),  (5)  fenestrate  membrane,  (6)  fibers  of  the  optic 
nerve,  (7)  trachece. 

The  cornea  (Fi.^'.  142)  is  a  l)icon\'ex  transparent  portion 
of  the  external  chitincuis  cuticiila.  Inimechately  beneath  it  are 
the  eone  eells,  which  ma}-  contain  a 
clear  liuid  or  else,  as  in  most  insects, 
solid  transparent  cones.  The  rhab- 
dom  is  a  transparent  chitinous  rod 
or  a  group  of  rods  {rhabdomeres) 
situated  in  the  long  axis  of  the 
ommatidium  and  surrounded  l:)y 
greatly  elongated  cells,  which 
constitute  the  retinula.  T  w  o 
zones  of  pigment  are  present :  an 
outer  zone,  of  iris  pigment,  in 
which  the  pigment  in  the  form  of 
fine  black  granules  is  contained 
chiefly  in  short  cells  that  surround 
the  retinula  distally ;  and  an  inner 
zone  of  retinal  pigment,  in  which 
the  pigment  cells  are  long  and 
slender,    and   enclose    the    retinula 

proximally.  All  these  parts  are  hjgDodermal  in  origin,  as  is  also 
the  fenestrate  basement  membrane,  through  which  pass  trachese 
and  nerve  fibers.  The  nerve  fibrill?e,  which  are  ultimate 
branches  of  the  optic  nerve,  pass  into  the  retinal  cells — the  end- 
organs  of  vision.  Under  the  basement  membrane  is  a  fibrous 
optic  tract  of  complex  structure. 

Physiology. — After  much  experimentation  and  discussion 
upon  the  physiology  of  the  compound  eye — the  subject  of  the 
monumental  works  of  Grenacher  and  Exner — Miiller's  "  mo- 
saic "  theory  is  still  generally  accepted,  though  it  was  proposed 
early  in  the  last  century.  It  is  thought  that  an  image  is 
formed  by  thousands  of  separate  points  of  light,  each  of  which 
corresponds  to  a  distinct  field  of  vision  in  the  external  world. 


Portion  of  compound  eye  of 
fly,  CalUphora  roinitoria,  radial 
section,  c,  cornea;  i,  iris  pig- 
ment; II,  nerve  fibers;  nc,  nerve 
cells;  r,  retinal  pigment;  t,  tra- 
chea.— After   HicKSON. 


ENTOMOLOGY 


Fig.  14: 


t    a 


Structure     of     an     omniatid- 
ium    of    Calliphora    vomitoria. 

A,  radial      section      (chiefly)  ; 

B,  transverse  section  through 
middle  region;  C,  transverse 
section  through  basal  region ; 
hm,  basement  membrane;  c, 
cornea;  n,  nucleus;  nv,  nerve 
fibrillae;    pc,    pseudocone;    pg^, 

pg'^,  cells  containing  iris  pig- 
ment; p^,  cell  containing  ret- 
inal pigment;  r,  one  of  the  six 


Each  ommatidium  is  adapted  to  trans- 
mit light  along  its  axis  only  (Fig. 
143).  as  oblique  rays  are  lost  by  ab- 
sorption in  the  black  pigment  which 
surrounds  the  crystalline  cone  and  the 
axial  rhabdom.  Along  the  rhabdom, 
then,  light  can  reach  and  affect  the 
terminations  of  the  optic  nerve.  Each 
ommatidium  does  not  itself  form  a 
picture ;  it  simply  preserves  the  inten- 
sity and  color  of  the  light  from  one 
particular  portion  of  the  field  of 
vision ;  and  when  this  is  done  by  hun- 
dreds or  thousands  of  contiguous  om- 
matidia,  an  image  results.  All  that 
the  painter  does,  who  copies  an  object, 
is  to  put  together  patches  of  light  in 
the  same  relations  of  quality  and  posi- 
tion that  he  finds  in  the  object  itself 
— and  this  is  essentially  what  the  com- 
pound eye  does,  so  far  as  can  be  in- 
ferred from  its  structure. 

Exner,  removing  the  cones  with  the 
corneal  cuticula  (in  La/»/>ym), looked 
through  them  from  behind  with  the 
aid  of  a  microscope  and  found  that  the 
images  made  by  the  separate  omma- 
tidia  were  either  very  close  together 
or  else  overlapped  one  another,  and 
that  in  the  latter  case  the  details  corre- 
sponded ;  in  other  words,  as  many 
as  twenty  or  thirty  ommatidia  may  co- 
operate to  form  an  image  of  the  same 
portion   of   the   field   of   vision ;   this 

retinal  cells  which  compose  the  retinula;  rh,  rhab- 
dom, composed  of  six  rhabdomeres;  t,  trachea;  tv, 
tracheal  vesicle. — After   Hickson. 


ANATOMY    AND    PHYSIOLOGY 


113 


"  superposition  "  image  being  correspondingly  bright — an  ad- 
vantage, probably,  in  the  case  of  nocturnal  insects. 

Large  convex  eyes  indicate  a  wide  field  of  vision,  while 
small  numerous  facets  mean  distinctness  of  vision,  as  Lubbock 
has  pointed  out.  The  closer  the  object  the  better  the  sight, 
for  the  greater  will  be  the  number  of 
lenses  employed  to  produce  the  impres- 
sion, as  Mollock  says.  If  Miiller's 
theory  is  true,  an  image  may  be  formed 
of  an  object  at  any  reasonable  distance. 
no  power  of  accommodation  being  ne- 
cessary; while  if,  on  the  other  hand, 
each  cornea  with  its  crystalline  cones 
had  to  form  an  image  after  the  manner 
of  an  ordinary  hand-lens,  only  objects 
at  a  definite  distance  could  be  imaged. 

The  limit  of  the  perception  of  form 
by  insects  is  placed  at  about  two  meters 
for  Lampyris,  1.50  meters  for  Lepi- 
doptera,  68  cm.  for  Diptera  and  58  cm. 
for  Hymenoptera. 

It  is  generally  agreed,  however,  tliat 
the  compound  eyes  are  specially  adapted 
to  perceive  movements  of  objects.  The 
sensitiveness  of  insects  to  even  slight 
movements  is  a  matter  of  common  ob- 
servation;  often,  however,  these  insects  can  be  picked  up  with 
the  fingers,  if  the  operation  is  performed  slowly  until  the  insect 
is  within  the  grasp.  A  moving  object  afifects  different  facets  in 
succession,  without  necessitating  any  turning  of  the  eyes  or  the 
head,  as  in  vertebrates.  Furthermore,  on  the  same  principle, 
the  compound  eyes  are  serviceable  for  the  perception  of  form 
when  the  insect  itself  is  moving  rapidly. 

The  arrangement  of  the  pigment  depends  adaptively  upon 
the  quality   of  the   light,   as    Stefanowska   and    Exner   have 
shown ;  thus,  when  the  light  is  too  strong,  the  iris  and  retinal 
9 


Diagram  of  outer,  trans- 
parent portion  of  an  omma- 
tidium  to  illustrate  the 
transmission  of  an  axial  ray 
(v4)  and  the  repeated  reflec- 
tion and  absorption  of  an 
oblique  ray  (B),  which  at 
length  emerges  at  C.  p,  iris 
pigment. 


I  14  ENTOMOLOGY 

pigment  cells  elongate  around  the  ommatidium  and  their  pig- 
ment granules  absorb  from  the  cone  cells  and  rhabdom  the 
excess  of  light.  If  the  light  is  weak,  they  shorten,  and  absorb 
but  a  minimum  amount  of  light. 

Origin  of  Compound  Eye. — The  compound  eye  is  often 
said  to  represent  a  group  of  ocelli,  chiefly  for  the  reason  that 
externally  there  appears  to  be  a  transition  from  simple  eyes, 
through  agglomerate  eyes,  to  the  facetted  type.  This  plausi- 
ble view,  however,  is  probably  incorrect,  for  these  reasons 
among  others.  In  the  ocellus,  a  single  lens  serves  for  all 
the  retinul^e,  while  in  the  compound  eye  there  are  as  many 
lenses  as  there  are  retinulae.  Moreover,  ocelli  do  not  pass 
directly  into  compound  eyes,  but  disappear,  and  the  latter  arise 
independently  of  the  former. 

Probably,  as  Grenacher  holds,  both  the  ocellus  and  the  com- 
pound eye  are  derived  from  a  common  and  simpler  type  of 
eye — are  ''  sisters,"  so  to  speak,  derived  from  the  same 
parentage. 

Perception  of  Light  through  the  Integument. — In  vari- 
ous insects,  as  also  in  earthworms,  blind  chilopods  and  some 
other  animals,  light  affects  the  nervous  system  through  the 
general  integument.  Thus  eyeless  dipterous  larvae  avoid  the 
light,  or,  more  precisely,  they  retreat  from  the  rays  of  shorter 
wave-length  (as  the  blue),  but  come  to  rest  in  the  rays  of 
longer  wave-length  (red),  as  if  they  were  in  darkness  (see 
page  350).  The  blind  cave-beetles  of  the  genus  Anophthal- 
imts  react  to  the  light  of  a  candle  (Packard).  Graber  found 
that  a  cockroach  deprived  of  its  eyesight  could  still  perceive 
light,  but  Lubbock  found  that  an  ant  whose  eyes  had  been 
covered  with  an  opaque  varnish  became  indifferent  to  light. 

Color  Sense. — Insects  undoubtedly  distinguish  certain  col- 
ors, though  their  color  sense  differs  in  range  from  our  own. 
Thus  ants  avoid  violet  light  as  they  do  sunlight,  but  probably 
cannot  distinguish  red  or  orange  light  from  darkness;  on 
the  other  hand,  they  are  extremely  sensitive  to  the  ultra-violet 
rays,   which   make  no  sensible  impression  upon   us.     Honey 


ANATOMY    AND    PHYSIOLOGY  I  I  5 

bees  frequently  select  Hue  flowers;  white  butterflies  (Pieris) 
prefer  white  flowers,  and  yellow  butterflies  (Colias)  appear 
to  alight  on  yellow  flowers  in  preference  to  white  ones  (Pack- 
ard). In  fact,  the  color  sense  is  largely  relied  upon  by  insects 
to  find  particular  flowers  and  l)y  butterflies  to  a  large  extent  to 
flntl  their  mates.     To  be  sure,  insects  will  visit  flowers  after 

Fig.  144- 


Alimentary  tract  of  a  collembolan,  Orchcsclla.  F,  fore  gut;  H,  hind  gut;  M,  mid 
gut;  c,  cardiac  valve;  cm,  circular  muscle;  Im.  longitudinal  muscle;  p,  pharynx;  py, 
pyloric  valve. 

the  brightly  colored  petals  have  been  removed  or  concealed, 
as  Plateau  found,  l;)ut  this  does  not  prove  that  the  colors  are 
of  no  assistance  to  the  insect,  though  it  does  show  that  they 
are  not  the  sole  attraction — the  odor  also  being  an  important 
guide. 

Problematical  Sense  Organs. — As  all  our  ideas  in  regard 
to  the  sensations  of  insects  are  necessarily  inferences  from  our 
own  sensory  experiences,  they  are  inevitably  inadequate. 
While  it  is  certain  that  insects  have  at  least  the  senses  of  touch, 
taste,  smell,  hearing  and  sight,  it  is  also  certain  that  these 
senses  of  theirs  differ  remarkably  in  range  from  our  own,  as 
we  have  shown.  We  can  form  no  accurate  conception  of  these 
ordinary  senses  in  insects,  to  say  nothing  of  others  that  insects 
have,  some  of  which  are  probably  peculiar  to  insects.  Thus 
they  have  many  curious  integumentary  organs  which  from 
their  structure  and  nerve  connections  are  probably  sensory 
end-organs,  though  their  functions  are  either  doubtful  or  un- 
known. Such  an  organ  is  the  sensillum  placodeum  (p.  95), 
the  use  of  which  is  very  doubtful,  though  the  organ  is  pos- 
sibly affected  by  air  pressure.     Insects  are  extremely  sensitive 


i6 


ENTOMOLOGY 


to  variations  of  wind,  temperature,  moisture  and  atmospheric 
pressure,  and  very  likely  have  special  end-organs  for  the  per- 
ception of  these  variations;  indeed,  the  sensilla  trichodea  are 
probably  affected  by  the  wind,  as  we  have  said. 

The  halteres  of  Diptera,  representing  the  hind  wings,  con- 
tain sensory  organs  of  some  sort.  They  have  been  variously 
regarded  as  olfactory  (Lee), auditory  (Graber),and  as  organs 
of  equilibration.  When  one  or  both  halteres  are  removed, 
the  fly  can  no  longer  maintain  its  equilibrium  in  the  air,  and 
Weinland  holds  that  the  direction  of  flight  is  affected  by  the 
movements  of  these  "  balancers." 

6.  Digestive  System 

The  alimentary  tract  in  its  simplest  form  is  to  be  seen  in 
Thysanura,  Collembola  and  most  larv?e,  in  which  (Fig.  144) 
it  is  a  simple  tube  extending  along  the  axis  of  the  body  and 


Alimentary  tract  of  a  grasshopper,  Melanophis  differentialis.  c,  colon;  cr,  crop; 
Sc,  gc,  gastric  caeca;  i,  ileum;  m,  mid  intestine,  or  stomach;  mt,  Malpighian,  or  kid- 
ney,  tubes;   o,  oesophagus;  p,  pharynx;   r,   rectum;   s,   salivary   gland  of  left  side. 


consisting  of  three  regions,  namely,  fore,  mid  and  Jiind  gut. 
These  regional  distinctions  are  fundamental,  as  the  embry- 
ology shows,  for  the  middle  region  is  entodermal  in  origin 
and  the  two  others  are  ectodermal,  as  appears  beyond. 

There  are  many  departures  from  this  primitive  condition, 
and  the  most  specialized  insects  exhibit  the  following-  modifi- 
cations (Figs.  145,  146)  of  the  three  primary  regions: 

Fore  intestine  {stoinodcruin)  :  mouth,  pharynx,  oesophagus, 
crop,  proventriculus  (gizzard),  cardiac  valve. 


ANATOMY    AND    PHYSIOLOGY 


117 


Fig.  146. 


Mid  iiifc'sfiiic  (incseiiteron)  :  ventriculus  (stomach). 

HiJhi  nitrstiiic   ( proctodmim)  :  pyloric  valve,  ileum,  colon, 
rectum,  aims. 

Stomodaeum. — The  mouth,  the  anterior  opening-  of  the 
food  canal,  is  to  be  dis- 
tinguished from  the 
pharynx,  a  dilatation  for 
reception  of  food.  In 
the  pharynx  of  mandib- 
ulate  insects  the  food  is 
acted  upon  by  the  saliva ; 
in  suctorial  forms  the 
pharynx  acts  as  a  pump- 
ing organ,  in  the  manner 
already  described. 

The  ocsopliagus  is  com- 
monly a  simple  tube  of 
small  and  uniform  cali- 
ber, varying  greatly  in 
length  according  to  the 
kind  of  insect.  Passing 
between  the  commissures 
that  connect  the  brain 
with  the  subcesophageal 
ganglion  (Fig.  113),  the 
oesophagus  leads  grad- 
ually or  else  abruptly 
into  the  crop  or  gizsard, 
or  when  these  are  absent, 
directly  into  the  stomach. 
In  addition  to  its  func- 
tion of  conducting  food, 
the  oesophagus  is  some- 
times glandular,  as  in  the  grasshopper,  in  which  it  is  said 
to  secrete  the  "molasses  "wliich  these  insects  emit. 


Digestive  system  of  a  beetle,  Carahus.  a, 
anal  gland;  c  (of  fore  gut),  crop;  c  (of 
hind  gut),  colon,  merging  into  rectum;  d, 
evacuating  duct  of  anal  gland;  g,  gastric 
caeca;  i,  ileum;  in,  mid  intestine;  mt,  Mal- 
pighian  tubes;  o,  oesophagus;  p,  proventricu- 
lus;   r,   reservoir. — After  Kolbe. 


ii8 


ENTOMOLOGY 


Fig.  147 


The  crop  is  conspicuous  in  most  Orthoptera  (Fig.  145)  and 
Coleoptera  (Fig.  146)  as  a  simple  dilatation.  In  Neuroptera 
(Fig.  147)  its  capacity  is  increased  by 
means  of  a  lateral  pocket — the  food  reser- 
voir; this  in  Lepidoptera,  Hymenoptera 
and  Diptera  is  a  sac  (Fig.  148,  c)  commu- 
nicating with  the  oesophagus  by  means  of 
a  short  neck  or  a  long  tube,  and  serving  as 
a  temporary  receptacle  for  food.  In  her- 
Ijivorous  insects  the  crop  contains  glucose 
formed  from  starch  by  the  action  of  saliva 
or  the  secretion  of  the  crop  itself;  in  car- 
nivorous insects  this  secretion  converts 
albuminoids  into  assimilable  peptone-like 
substances. 

Next  comes  the  enlargement  known  as 
the  prorciitriciiliis,  or  gi:;::ard,  which  is 
present  in  many  insects,  especially  Orthop- 
tera and  Coleoptera    (Fig.    146),  and  is 
usually  found  in  such  mandibulate  insects 
as  feed  upon  hard  substances.     The  pro- 
ventriculus  is  lined  with  chitinous  teeth  or 
ridges    for   straining  the   food,   and   has 
powerful  circular  muscles  to  squeeze  the 
food  back  into  the  stomach,  as  well  as 
longitudinal  muscles  for  relaxing,  or  open- 
ing, the  gizzard.     Some  authors  maintain  that  the  proventricu- 
lus  not  only  serves  as  a  strainer,  but  also  helps  to  comminute 
the  food,  like  the  gizzard  of  a  bird. 

In  most  insects  a  cardiac  valve  guards  the  entrance  to  the 
stomach,  preventing  the  return  of  food  to  the  gullet.  This 
valve  (Figs.  144,  149)  is  an  intrusion  of  the  stomodseum  into 
the  mesenteron,  forming  a  circular  lip  which  permits  food  to 
pass  backward,  but  closes  upon  pressure  from  behind. 

Mesenteron. — The    vciitricuhis,    otherwise   known    as    the 


Digestive  system  of 
Myrmeleon  larva.  c, 
csecum;  cr,  crop;  m,  mid 
intestine;  mt,  Malpighian 
tubes;  s,  spinneret. — 
After   Meinert. 


ANATOMY    AND    PHYSIOLOGY 


119 


mid  intestine,  or  stomach,  is  usually  a  simple  tube  of  large 
caliber,  as  compared  with  the  oesophagus  or  intestine,  and  into 

Fig.  148. 


cm 


Alimentary  tract  of  a  moth,  Sphinx,  c,  food  reservoir;  cl,  colon;  cm,  caecum;  i,  ileui 
m,  mid  intestine;  mt,  Malpighian  tubes;  o,  a-sophagus;  r,  rectum;  s,  salivary  gland. 
After  Wagner. 


the  ventriculus  may  open  glandular  blind  tubes 
cccca  (Figs.  145.  146)  ;  these,  though 
numerous  in  some  insects,  are  commonly 
few  in  number  and  restricted  to  the  ante- 
rior region  of  the  stomach.  The  gastric 
c?eca  of  Orthoptera  secrete  a  weak  acid 
^^•hich  emulsifies  fats,  or  one  which  passes 
forward  into  the  crop,  there  to  act  upon 
albuminoid  substances.  In  the  stomach 
the  food  may  be  acted  upon  by  a  fluid 
secreted  by  specialized  cells  of  the  epithe- 
lial wall.  In  various  insects,  certain  cells 
project  periodically  into  the  lumen  of  the 
stomach  as  papillse,  which  by  a  process  of 
constriction  become  separated  from  the 
parent  cells  and  mix  bodily  with  the  food. 
This  phenomenon  takes  place  in  the  larva 
of  Ptychoptera  (van  Gehuchten),  also  in 
nymphs  of  Odonata  (Needham),  and  is 
probably  of  widespread  occurrence  among 
insects.       The     chief     function     of     the 


Cardiac  valve  of  young 
muscid  larva,  o,  cesoph- 
agus;  p,  proventriculus; 
z',  valve.  In  an  older 
larva  the  valve  projects 
into  the  mid  intestine. — 
After  KowALEVSKY. 


I20 


ENTOMOLOGY 


Stomach,  however,  is  absorption,  which  is  effected  by  the 
general  epithehum.  Physiologically,  the  so-called  stomach  of 
an  insect  is  quite  unlike  the  stomach  of  a  vertebrate,  being  more 
like  an  intestine. 

Proctodasum. — At  the  anterior  end  of  the  hind  intestine 
there  is  usually  a  pyloric  valve,  which  prevents  the  contents  of 
the  intestine  from  returning  into  the  stomach.  This  valve  may 
operate  by  means  of  a  sphincter,  or  constricting,  muscle,  or 
may,  as  in  Collembola  (Fig.  144),  con- 
sist of  a  backward-projecting  circular 
ridge,  or  lip.  which  closes  upon  pressure 
from  behind. 

In  its  primitive  condition  the  hind 
intestine  is  a  simple  tube  (Fig.  144). 
Usually,  however,  it  presents  two  or 
even  three  specialized  regions,  namely 
and  in  order,  ileum,  colon  and  rectum 
(Fig.  145).  The  hind  intestine  varies 
greatly  in  length  and  is  frecjuently  so 
long  as  to  be  thrown  into  convolutions 
(Fig.  150).  The  ileum  is  short  and 
stout  in  grasshoppers  (Fig.  145)  ;  long, 
slender  and  convoluted  in  many  carniv- 
orous beetles ;  and  quite  short  in  cater- 
pillars and  most  other  larvje ;  its  func- 
tion is  absorption.  The  colon,  often 
absent,  is  evident  in  Orthoptera  and 
Lepidoptera  and  may  bear  (Bencicus, 
Dytiscus,  Silphidse,  Lepidoptera)  a  con- 
spicuous cjecal  appendage  (Figs.  148,  150)  of  doubtful  func- 
tion, though  possibly  a  reservoir  for  excretions.  The  colon 
contains  indigestible  matter  and  the  waste  products  of  diges- 
tion, including  the  excretions  of  the  Malpighian  tubes.  The 
rectum  (Fig.  145)  is  thick-walled,  strongly  muscular  and  often 
folded  internally.  Its  office  is  to  expel  excrementitious  matter, 
consisting  largely  of  the  indigestible  substances  chitin,  cellulose 


Digestive  system  of  Belos- 
toma.  c,  caecum;  i,  ileum; 
m,  mid  intestine;  mt,  Mal- 
pighian tubes;  r,  salivary 
reservoir;  s,  salivary  gland. 
— After  LocY,  from  the 
American    Naturalist. 


ANATOjMY    AND    PHYSIOLOGY 


121 


and  chlorophyll.  The  rectum  terminates  in  the  anus,  which 
opens  throug-h  the  last  segment  of  the  ahdomen,  always  above 
the  g"enital  apertnre. 

Histology. — The  epithelial  wall  of  the  alimentary  tract  is 
a  single  layer  of  cells  (Fig.  151).  which  secretes  the  intima, 
or  lining  layer,  and  the  basement  mcuihranc — a  delicate,  struc- 
tureless enveloping  layer. 
The  intima,  which  is  contin- 
uous with  the  external  cutic- 
ula,  is  chitinous  in  the  fore 
and  hind  gut  (which  are 
ectodermal  in  origin),  but 
not  in  the  mid  gut  (entoder- 
mal),  and  usually  exhibits 
extremely  fine  transverse 
stri?e,  which  are  due  prob- 
ably to  minute  pore  canals. 
Surrounding  the  basement 
membrane  is  a  series  of  cir- 
cular muscles  and  outside 
these  is  a  layer  of  longitudi- 
nal muscles.  The  circular 
muscles  serve  to  constrict  the  pharynx  in  sucking  insects 
and,  in  general,  to  squeeze  backward  the  contents  of  the 
alimentary  canal  by  successively  reducing  its  caliber.  The 
longitudinal  muscles,  restricted  almost  entirely  to  the  mid 
intestine,  act  in  opposition  to  the  constricting  muscles  to  en- 
large the  lumen  of  the  food  canal  and  in  addition  to  efifect 
peristaltic  movements  of  the  stomach. 

The  intima  of  the  crop  is  sometimes  shaped  into  teeth,  and 
that  of  the  proventriculus  is  heavily  chitinized  and  variously 
modified  to  form  spines,  teeth  or  ridges. 

Salivary  Glands. — In  their  simplest  condition,  the  salivary 
glands  are  a  pair  of  blind  tubes  (Fig.  152),  one  on  each  side 
of  the  oesophagus  and  opening  separately  at  the  base  of  the 
hypopharynx.     Commonly,  however,  the  glands  open  through 


W'all  of  mid  intestine  of  silk  worm, 
transverse  section,  b,  basement  membrane; 
c,  circular  muscle;  i,  intima;  /,  longitudinal 
muscle;  n,  n,  nuclei  of  epithelial  cells;  s, 
secretory   cell. 


ENTOMOLOGY 


Fig.  152. 


g 


two  salivary  ducts  into  a  common,  or  evacuating,  duct ;  a  pair 
of  salivary  reservoirs  (Fig.  153)  may  be 
present,  and  the  glands  are  frequently 
branched  or  lobed,  and,  though  usually 
confined  to  the  head,  may  extend  into  the 
thorax  or  even  into  the  abdomen. 

Many  insects  have  more  than  one  pair 
of  glands  opening  into  the  pharynx  or 
oesophagus ;  thus  the  honey  bee  has  six 
pairs  and  Hymenoptera  as  a  whole  have 
as  many  as  ten  different  pairs.  Though 
all  these  are  loosely  spoken  of  as  salivary 
glands,  it  is  better  to  restrict  that  term  to 
the  pair  of  glands  that  open  at  the  hypo- 
pharynx. 

All  these  cephalic  glands  are  evagina- 
tions  of  the  stomodseum  (ectodermal  in 
origin)  and  consist  of  an  epithelial  layer 
with  the  customary  intima  and  basement 
membrane  (Fig.  154).  The  nuclei  are 
large,  as  is  usually  the  case  in  glandular 
cells,  and  the  cytoplasm  consists  of  a  dense 
framework  (appearing  in  sections  as  a 
network)  enclosing  vacuoles  of  a  clear 
substance — the  secretion;  the  chitinous 
Fig. 


A  simple  salivary 
gland  of  Cacilius.  c, 
canal;  (/,  duct;  g,  g,  gland- 
ular   cells. — After    Kolbe. 


Right    salivary    gland    of    cockroach,    ventral    aspect,     c,    common    duct;    g,    gland;    h, 
hypopharynx;  r,  reservoir. — After  Miall  and  Denny. 


ANATOMY    AND    PHYSIOLOGY 


123 


Histology  of  salivary  gland 
of  Cacilius,  radial  section.  h, 
basement  membrane;  c,  canal; 
g,  glandular  cell;  i,  intima;  n, 
nucleus. — After    Kolbe. 


intima  is  penetrated  by  fine  pore  canals  through  which  the 
secretion  passe.^.  In  many  insects,  notably  the  cockroach,  the 
common  duct  is  held  distended  by 
spiral  threads  which  give  the  duct 
much  the  appearance  of  a  tra- 
chea. 

In  herbivorous  insects  the  saliva 
changes  starch  into  glucose,  as  in 
vertebrates;  in  carnivorous  forms  it 
acts  on  proteids  and  is  often  used 
to  poison  the  prey,  as  in  the  larva 
of  Dytiscits.  In  the  mosquito  each 
gland  is  three-lobed  (Fig.  155)  ;  the 
middle  lobe  is  different  in  appearance 
from  the  two  others  and  secretes 
a  poisonous  fluid  which  is  carried  out 
along  the  hypopharynx.  Though  this  poison  is  said  to  facili- 
tate the  process  of  blood-sucking  by  preventing  the  coagulation 
of  the  blood,  its  primary  use  was  perhaps  to  act  upon  proteids 
in  the  juices  of  plants. 

Malpighian  Tubes. — The  kidney,  or  Malpighian,  tubes, 
present  in  nearly  all  insects,  are  long,  slender,  blind  tubes  open- 
ing into  the  intestine  imme- 
diately behind  the  stomach 
as  a  rule  (Figs.  145,  146), 
but  always  into  the  intestine. 
The  number  of  kidney  tubes  is 
very  different  in  different  in- 
sects; Collembola  have  none, 
while  Odonata  have  fifty  or  more  and  Acridiid?e  as  many  as 
one  hundred  and  fifty;  commonly,  however,  there  are  four  or 
six,  as  in  Coleoptera,  Lepidoptera  and  many  other  orders. 
Not  more  than  six  and  frequently  only  four  occur  in  the  em- 
bryo (Wheeler),  though  these  few  embryonic  tubes  may  sub- 
sequently branch  into  many. 


One  of  the  three-lobed  salivary  glands 
of  a  mosquito.  The  middle  lobe  secretes 
the  poison. — After  Macloskie,  from  the 
American   Naturalist. 


124 


ENTOMOLOGY 


Fig.  156. 


The  Malpighian  tubes  (Fig.  156)  are  evaginations  of  the 
proctodaeum  and  are  consequently  ectodermal.  A  cross  sec- 
tion of  a  tube  shows  a  ring  of  from  one 
to  six  or  more  large  polygonal  cells  (Fig. 
157),  which  often  project  into  the  lumen 
of  the  tube ;  the  nuclei  are  usually  large 
and  may  be  branched,  as  in  Lepidoptera. 
A  chitinous  intima,  traversed  by  pore- 
canals,  lines  the  tube,  and  a  delicate  base- 
ment membrane  is  present,  surrounded 
by  a  peritoneal  layer  of  connective  tissue. 
Furthermore,  the  urinary  tubes  are  richly 
supplied  with  tracheae.  In  function,  the 
Malpighian  tubes  are  analogous  to  the 
vertebrate  kidneys  and  contain  a  great 
variety  of  substances,  chief  among 
which  are  uric  acid  and  its  derivatives 
(such  as  urate  of  sodium  and  of  ammo- 
nium), calcium  oxalate  and  calcium  car- 
bonate. 

Parts    of    the    fat-body    may    also    be 
concerned    in    excretion ;    thus    the    fat- 
body   in    Collembola   and    Orthop-  pj^,   ^ry 
tera  serves  for  the  permanent  stor- 
age of  urates. 

7.  Circulatory  System 
Insects,  unlike  vertebrates,  have 
no  system  of  closed  blood-vessels, 
but     the     blood     wanders     freely 
through  the  body  cavity  to  enter      cross  section  of  Malpighian  tube 
eventually  the  dorsal  vessel,  which   ^^    silkworm,    Bombyx    mori.    b, 

.  .  basement    membrane;    c,    crystals;    i, 

resembles  a  heart  merely  in  bemg  intima;  /,  lumen;   n,  nucleus;  p. 

a  propulsatory  organ.        '  peritoneal  layer.     Greatly  magnified. 

Dorsal  Vessel. — The  dorsal  vessel  (Figs.  158,  162)  is  a 


Portion  of  Malpighian 
tube  of  caterpillar,  Samia 
cecropia,    surface   view. 


ANATOMY    AND    PHYSIOLOGY 


ately  under  the  integ^ument.     A  simple  tube  in  some  larvcT,  it 
consists  in  most  adults  chiefly  of  a  series  of  chambers,  each  of 

Fig.  158. 


Dorsal  vessel  of  beetle, 
Lucantis.  a,  aorta;  al,  alary 
muscle;  o,  ostium.  —  After 
Steaus-Durckheim. 


Diagram  of  a  portion  of  the  heart  of  a  dragon 
fly  nymph,  Epithcca.  o,  ostium;  z;  valve;  the  ar- 
rows  indicate    the   course  of      the      blood.  —  After 

KoLBE. 

Fig.  160. 


Diagrammatic  cross  section  of  pericardial 
region  of  a  grasshopper,  Qidipoda.  a,  alary 
muscle;  d,  dorsal  vessel;  s,  suspensory  mus- 
cles;  sp,   septum. — After   Graber. 


Blood   corpuscles  of   a  grasshopper,   Stoiobotltnis.     a~f,   corpuscles   covered   witli    fat- 
globules;  g,  corpuscle  after  treatment  with  glycerine,  showing  nucleus. — After  Graber. 


which  has  on  each  side  a  valvular  opening,  or  ostium   (Fig. 
159) ,  which  permits  the  ingress  of  blood  but  opposes  its  egress ; 


126 


ENTOMOLOGY 


within  the  chambers  occur  other  valvular  folds  that  allow  the 
blood  to  move  forward  only.  With  few  exceptions  (Ephe- 
meridcx)  the  dorsal  vessel  is  blind  behind  and  the  blood  can 
enter  it  only  through  the  lateral  ostia. 

Aorta. — The  posterior,  or 
pulsating  portion  (heart)  of 
the  dorsal  vessel  is  confined 
for  the  most  part  to  the  abdo- 
men ;  the  anterior  portion,  or 
aorta,  extends  as  a  simple 
attenuated  tube  through  the 
thorax  and  into  the  head, 
where  it  passes  under  the 
brain  and  usually  divides  into 
two  l)ranches  (Fig.  162), 
each  of  which  may  again 
branch.  In  the  head  the 
blood  leaves  the  aorta  ab- 
ruptly and  enters  the  general 
body  cavity. 

Alary    Muscles. — Extend- 
ing outward  from  the  "heart," 
or  propulsatory  portion,  and 
making  with  the  dorsal  wall 
of     the    body     a     pericardial 
chamber,  is  a  loose  diaphragm, 
formed  largely  by  paired  fan-like  muscles — the  alary  muscles 
(Eigs.  158,  160).     These  are  thought  to  assist  the  heart  in  its 
propulsatory  action. 

Structure  of  the  Heart. — The  dorsal  vessel  has  a  delicate 
lining-membrane,  or  intima,  and  a  thin  enveloping  membrane; 
between  these,  in  the  heart,  is  a  layer  of  fine  muscle  fibers,  cir- 
cular or  spiral  in  direction,  which  efifect  the  contractions  of  the 
organ. 

Ventral  Sinus. — In  many  if  not  most  insects  a  pulsatory 
septum  (Fig.  177,  v)  extends  across  the  floor  of  the  body  cav- 


r^ 


Diagram  to  indicate  the  course  of  the 
blood  in  the  nymph  of  a  dragon  fly, 
Epitheca.  a,  aorta;  h,  heart;  the  arrows 
show  directions  taken  by  currents  of 
blood. — After  Kolbe. 


ANATOMY    AND    PHYSIOLOGY  I  2/ 

ity  to  form  a  sinus,  in  wliicli  tlic  blood  flows  backward,  batbiiio- 
the  ventral  nerve  cord  as  it  "'oes.  Tliis  ventral  sinus  supple- 
ments the  heart  in  a  minor  way,  as  do  also  the  local  pulsatory 
sacs  which  ha\e  l)een  discovered  in  the  lei^'s  of  arjuatic  Hemip- 
tera  and  the  head  of  Orthoptera. 

Blood. — The  blood,  or  hcumolyinph,  of  an  insect  consists 
chielly  of  a  watery  fluid,  or  plasma,  which  contains  corpuscles, 
or  leucocytes.  Thoug-h  usually  colorless,  the  plasma  is  some- 
times A^ellow  (Coccinellidrc,  Meloidre),  often  greenish  in  her- 
bivorous insects  from  the  presence  of  chlorophyll,  and  some- 
times of  other  colors ;  often  the  blood  owes  its  hue  to  yellow 
or  red  drops  of  fat  on  the  surface  of  the  blood  corpuscles 
(Fig.  i6i). 

Leucocytes. — The  corpuscles,  or  leucocytes,  are  minute 
nucleated  cells,  6  to  30  ;«■  in  diameter,  variable  in  form  even 
in  the  same  species  but  commonly  (Fig.  161)  round,  oval  or 
ovate  in  profile,  though  often  disk-shaped,  elongate  or  amoe- 
boid in  form. 

Function  of  the  Blood. — The  blood  of  insects  contains 
many  substances,  including  egg  albumin,  globulin,  fibrin,  iron, 
potassium  and  sodium  (Mayer),  and  especially  such  a  large 
amount  of  fatty  material  that  its  principal  function  is  probably 
one  of  nutrition;  the  blood  of  an  insect  contains  no  red  cor- 
puscles and  has  little  or  nothing  to  do  with  the  aeration 
of  tissues,  that  function  being  relegated  to  the  tracheal 
system. 

Circulation. — The  course  of  the  circulation  is  evident  in 
transparent  aquatic  nymphs  or  larv?e.  In  odonate  or  ephe- 
merid  nymphs,  currents  of  blood  may  be  seen  (Fig.  162)  flow- 
ing through  the  spaces  between  muscles,  tracheze,  nerves,  etc., 
and  bathing  all  the  tissues;  separate  outgoing  and  incoming 
streams  may  be  distinguished  in  the  antennae  and  legs;  the 
returning  blood  flows  along  the  sides  of  the  body  and  through 
the  ventral  sinus  and  the  pericardial  chamber,  eventually  to 
enter  the  lateral  ostia  of  the  dorsal  vessel.  A  circulation  of 
blood  occurs  in  the  wings  of  freshly  emerged  Odonata.  Ephe- 


128  ENTOMOLOGY 

merida,  Coleoptera,  Lepidoptera,  etc.,  the  currents  trending 
along-  the  tracheje;  this  circulation  ceases,  however,  with  the 
drying  of  the  wings. 

The  chambers  of  the  dorsal  vessel  expand  and  contract  suc- 
cessively from  behind  forward.  At  the  expansion  (diastole) 
of  a  chamber  its  ostia  open  and  admit  blood ;  at  contraction 
(systole)  the  ostia  close,  as  well  as  the  valve  of  the  chamber 
next  behind,  while  the  chamber  next  in  front  expands,  afford- 
ing the  only  exit  for  the  blood.  The  valves  close  partly 
through  blood-pressure  and  partly  by  muscular  action. 

The  rate  of  pulsation  depends  to  a  great  extent  upon  the 
activity  of  the  insect  and  upon  the  temperature  and  the  amount 
of  oxygen  or  carbonic  acid  gas  in  the  surrounding  atmosphere. 
Oxygen  accelerates  the  action  of  the  heart  and  carbonic  acid 
gas  retards  it.  A  decrease  of  8°  or  io°  C.  in  the  case  of  the 
silkworm  lowers  the  number  of  beats  from  30  or  40  to  6  or 
8  per  minute.  The  more  active  an  insect,  the  faster  its  heart 
beats. 

The  rate  of  pulsation  is  very  different  in  the  different  stages 
of  the  same  insect.  Thus  in  Sphinx  ligustri,  according  to 
Newport,  the  mean  number  of  pulsations  in  a  moderately 
active  larva  before  the  first  moult  is  about  82  or  83  per  minute ; 
before  the  second  moult,  89,  sinking  to  63  before  the  third 
moult,  to  45  before  the  fourth,  and  to  39  in  the  final  larval 
stage;  the  force  of  the  circulation,  however,  increases  as  the 
pulsations  decrease  in  number.  During  the  quiescent  period 
immediately  preceding  each  moult,  the  number  of  beats  is 
about  30.  In  the  pupal  stage  the  number  sinks  to  22,  and 
then  lowers  until,  during  winter,  the  pulsations  almost  cease. 
The  moth  in  repose  shows  41  to  50  per  minute,  and  after  flight 
as  many  as  139. 

8.  Fat-Body 

The  fat-body  appears  (Fig.  163)  as  many-lobed  masses  of 
tissue  filling  in  spaces  between  other  organs  and  occupying  a 
large  part  of  the  body  cavity.  The  distribution  of  the  fat- 
body  is  to  a  certain  extent  definite,  however,  for  the  fat-tissue 


ANATOMY    AND    PHYSIOLOGY 


129 


conforms  to  the  general  segmentation  and  is  arranged  in  each 
segment  with  an  ap]irf\'ich  to  symmetry.  Much  of  this  tissue 
forms  a  distinct  peripheral  layer  in  each  segment,  and  masses 
of  fat-hody  occur  constantly  on  each  side  of  the  alimentary 


Transverse  section  of  the  abdomen  of  a  caterpillar,  Picris  rapcr.  b,  blood  corpus- 
cles; c,  cuticula;  d,  dorsal  vessel;  f,  fat-body;  g,  ganglion;  /;,  hypodermis;  /,  leg;  m, 
muscle;  mi,  mid  intestine,  containing  fragments  of  cabbage  leaves;  mt,  Malpighian 
tube;  s,  silk  gland;  sp,   spiracle;   tr,  trachea. 


tract  and  also  at  the  sides  of  the  dorsal  vessel,  in  the  latter  case 
forming  the  pericardial  fat-body. 

Fat-Cells. — The  fat-cells  (Fig.  164)  are  large  and  at  first 
more  or  less  spherical,  with  a  single  nucleus  (though  there  are 
said  to  be  two  in  Apis  and  several  in  Musca),  l)ut  the  cellular 
10 


30 


ENTOMOLOGY 


Fat-cells  of  a  caterpillar,  Pieris. 
cells  filled  with  drops  of  fat;  B,  cell 
freed  of  fat-drops,  showing  nucleus. — 
After  KoLBE. 


Structure  of  the  fat-tissue  is  often  difficult  to  make  out  because 
the  cells  are  usually  filled  with  globules  of  fat    (Fig.   165), 

while  old  cells  break  down, 
leaving  only  a  disorderly  net- 
work. The  fat-cells  sometimes 
contain  an  albuminoid  sub- 
stance, and  usually  the  fat-body 
includes  considerable  quantities 
of  uric  acid  or  its  derivatives, 
frequently  in  the  form  of  con- 
spicuous concretions. 
Functions. — The  physiology  of  the  fat-system  is  still  ob- 
scure. Probably  the  fat-body  combines  several  functions.  In 
caterpillars  and  other  larvje  it  furnishes  a  reserve  supply  of 
nutriment,  at  the  expense  of  which  the  metamorphosis  takes 
place;  the  amount  of  fat  increases  as  the  larva  grows,  and 
diminishes  in  the  pupal  stage,  though  some  of  it  lasts  over  to 
furnish  nourishment  for  the  imago  and  its  germ  cells.  The 
gradual  accumulation  of  uric 

acid  and  urates  in  the  fat-  ^^^-  ^^5- 

body  indicates  an  excretory 
function,  particularly  in  Col- 
lembola,  which  have  no  Mal- 
pighian  tubes.  The  intimate 
association  between  the  ulti- 
mate tracheal  branches  and 
the  fat-body  has  led  some 
authorities  to  ascribe  a  res- 
piratory function  to  the  lat- 
ter. A  close  relation  of 
some  sort  exists  also  be- 
tween the  fat-system  and 
the  blood-system ;  fat-cells 
are  found  free  in  the  blood, 

and  the  blood  corpuscles  originate  in  the  thorax  and  abdo- 
men   from    tissues    that   can   scarcely   be   distinguished    from 


Section  through  fat-body  of  a  silkworm, 
showing  nucleated  cells,  loaded  with  drops 
of  fat. 


ANATOMY    AND    PHYSIOLOGY 


131 


ffinocytes  and  accom- 
panying trachea,  from 
abdomen  of  a  silkworm. 


fat-tissues.  The  corpuscles  (leucocytes,  or  phagocytes)  which 
in  some  insects  absorb  effete  larval  tissues  during-  meta- 
morphosis have  been  by  some  authors  reg'arded  as  wandering 
fat-cells.  Cells  cc^nstiluting  the  pericardial  fat-body  are  at- 
tached to  the  lateral  muscles  (alary  muscles)  of  the  dorsal 
vessel,  but  almost  nothing  is  known  as 
to  their  function.  Associated  with  the 
fat-body  proper  are  the  peculiar  cells 
known  as  a^iiocytes.  These  occur  in 
most  insects,  in  segmentally-arranged 
clusters  on  each  side  of  the  abdomen, 
and  consist  of  exceptionally  large  cells, 
more  or  less  rcnnid  or  oval  (Fig.  166), 
each  with  a  large  round,  oval  or  elon- 
gate nucleus.  These  peculiar  cells  are 
usually  separate  from  one  another,  but 
are  held  in  clusters  by  tracheal  branches. 
Their  function  is  unknown.     Finally,  the 

fat-body  is  the  basis  of  the  luminosity,  or  so-called  phospho- 
rescence, of  insects. 

Luminosity. — This  phenomenon  appears  sporadically  and 
by  various  means  in  protozoans,  worms,  insects,  fishes  and 
other  animals.  Luminosity  in  insects,  though  sometimes 
merely  an  incidental  and  pathological  effect  of  bacteria,  is  usu- 
ally produced  by  special  organs  in  which  light  is  generated 
probably  by  the  oxidation  of  a  fatty  substance. 

There  are  not  many  luminous  insects.  Those  best  known 
are  the  Mexican  and  West  Indian  beetles  of  the  genus  Py- 
rophorus  (Elateridie),  in  which  the  pronotum  bears  a  pair  of 
luminous  spots,  and  the  common  fire-tiies  (Lampyridse).  In 
Lampyrid?e,  the  light  is  emitted  from  the  ventral  side  of  the 
posterior  abdominal  segments.  In  our  common  Photinus,  the 
seat  of  the  light  is  a  modified  portion  of  the  fat-body — a 
photogenic  plate,  situated  immediately  under  the  integument 
and  supplied  with  a  profusion  of  fine  tracheal  branches.  The 
cells  of  the  photogenic  plate,  it  is  said,  secrete  a  substance  which 


132 


ENTOMOLOGY 


undergoes  rapid  combustion  in  the  rich  supply  of  oxygen  fur- 
nished by  the  tracheae. 

The  rays  emitted  by  the  common  fire-flies  are  remarkable  in 
being  almost  entirely  light  rays,  with  almost  no  thermal  or 

actinic  rays.  According  to 
Young'  and  Langley,  the  radia- 
tions of  an  ordinary  gas-tlame 
contain  less  than  three  per  cent. 
of  visible  rays,  the  remainder 
being  heat  or  chemical  rays,  of 
no  value  for  illuminating  pur- 
poses ;  while  the  light-giving 
efficiency  of  the  electric  arc  is 
only  ten  per  cent,  and  that  of 
sunlight  only  thirty-live  per 
cent.  The  light  of  the  fire- 
fly, however,  may  be  rated  at 
one  hundred  per  cent. ;  this 
light,  then,  is  perfect,  and  as 
yet  unapproached  by  artificial 
means. 

As  to  the  use  of  this  lumi- 
nosity, there  is  a  general 
opinion  that  the  light  exists 
for  the  purpose  of  sexual 
attraction — a  belief  held  by 
the  author  in  regard  to  Pho- 
tiiiiis,  at  least.  Another  view 
is  that  the  light  is  a  warning 


Tracheal    system    of    an    insect,     a,    an 
tenna;    b,    brain;    /,    leg;    n,    nerve    cord 

p,    palpus;    .,    spiracle;    .f     spiracular,    or     ^j  j    ^^^    nOCtumal    birds,    batS 

,  branch;   t,  mam  tracheal  trunk;  ^ 


stigmatal 

V,   ventral   branch 

After  KoLBE. 


isceral    branch.- 


)r  other  insectivorous  animals: 
this  is  supported  by  the  fact 
that  lampyrids  are  refused  Ijy  birds  in  general,  after  ex- 
perience; young  birds  readily  snap  at  a  fire-fly  for  the  first 
time,  but  at  once  reject  it  and  thereafter  pay  no  attention  to 
these  insects. 


ANATOMY    AND    PHYSIOLOGY 


133 


9.  Respiratory  System 
In  insects,  as  contrasted  with  vertebrates,  the  air  itself  is 
conveyed  to  tlic  remotest  tissues  l)y  means  of  an  elaborate  sys- 
tem (vf  branchins^-  air-tubes,  or  Iraclwcc,  which  receive  air 
throui^h  paired  se^nientally-arran£j;e(l  sf^irnclcs.  Each  spiracle 
is  commonly  the  mouth  of  a  short  tube  which  opens  into  a 
main  tracheal  trunk   (Fig.   167)   extending  along  the  side  of 


Diagrammatic  cross  section  of  the  thorax  of  an  insect,  a,  alimentary  canal;  d, 
dorsal  vessel;  g,  ganglion;  ,?,  spiracle;  zv,  wing;  /,  dorsal  tracheal  branch;  3,  visceral 
branch;  ^,  ventral  branch. 

the  body.  From  the  two  main  trunks  branches  are  sent  which 
divide  and  subdivide  until  they  become  extremely  delicate 
tubes,  which  penetrate  even  between  muscle  fibers,  between  the 
ommatidia  of  the  compound  eyes  and  possibly  enter  cells.  In 
most  cases  each  main  longitudinal  trunk  gives  off  in  each  seg- 
ment (Fig.  i68)  three  large  branches:  (  i)  an  upper,  or  dor- 
sal, branch,  which  goes  to  the  dorsal  muscles;  (2)  a  middle, 
or  visceral,  branch,  which  supplies  the  alimentary  tract  and  the 
reproductive  organs;  (3)  a  lower,  or  ventral,  branch,  which 
pertains  to  the  ventral  ganglia  and  muscles. 

In  many  swiftly-flying  insects  (dragon  flies,  beetles,  moths, 
flies  and  bees)  there  occur  tracheal  pockets,  or  air-sacs,  which 


134 


ENTOMOLOGY 


Fig.   169. 


were  formerly  and  erroneously  supposed  to  diminish  the 
weight  of  the  insect,  but  are  now  regarded  as  simply  air- 
reservoirs. 

Types  of  Tracheation. — Two  types  of  tracheal  system  are 
distinguished    for   convenience :    ( i )    The   primary,   open,   or 

Iwlopncustic  type  described 
above,  in  which  the  spiracles 
are  functional;  (2)  the  sec- 
ondary, closed,  or  apncitstic 
type,  in  which  the  spiracles 
are  either  functionless  or  ab- 
sent. This  type  is  illustrated 
in  Collembola  and  such  acjuatic 
nymphs  and  larvae  as  breathe 
either  directly  through  the  skin 
or  else  by  means  of  gills. 
The  two  types,  howe\'er,  are 
connected  by  all  sorts  of  inter- 
mediate stages. 

Tracheal    Gills. — In    manv 


Lateral  gill  from  abdomen  of  a  May 
fly  nymph,  Hcxagcnia  variabilis.  En- 
larged. 


acjuatic  nymphs  and  larva?  the 

spiracles  are  suppressed    (though  they  become  functional  in 

the  imago)  and  respiration  is  effected  by  means  of  gills;  these 

are  cuticular  outgrowths  which  usuallv,  ^ 

^  .  '  Fig.  170. 

though  not  invariably,   contain  tracheae, 

and  are  commonly  lateral  or  caudal  in 
position.  Lateral  tracheal  gills  are 
highly  developed  in  ephemerid  nymphs 
(Fig.  169),  in  which  a  pair  occurs  on 
some  or  all  of  the  first  seven  segments 
of  the  abdomen ;  a  few  genera,  how- 
ever, have  cephalic  or  thoracic  gills.  Larvae  of  Trichoptera 
have  paired  abdominal  gills  varying  greatly  in  form  and  posi- 
tion, and  Perlidae  often  have  paired  thoracic  gills.  Caudal 
traclieal  gills  are  conspicuous  in  nymphs  of  Agrionidae  (Fig. 
170)    as   three   foliaceous   appendages.     A   few   coleopterous 


Caudal      gills      of 
agrionid         nyniph, 
larged. 


ANATOMY    AND    PHYSIOLOGY 


135 


larxcT  of  cuiiiatic  hal)it,  as  Gyriuits  and 
Ciicniidofiis,  possess  tracheal  gills,  as  do 
also  caterpillars  of  the  g'eniis  Paniponyx 
{V\g.  171).  which  feed  011  the  leaves  of 
several  kinds  of  water  plants. 

Though  manifold  in  form,  tracheal 
g'ills  are  generally  more  or  less  foliaceous 
or  filamentous,  presenting  always  an  ex- 
tensive respiratory  surface ;  their  integu- 
ment is  thin  and  the  tracheae  spread 
closely  beneath  it.  These  adaptations 
are  often  supplemented  by  waving  move- 
ments of  the  gills,  as  in  May  fly  nymphs, 
and  by  frequent  movements  of  the  insect 
from  one  place  to  another. 

Especially  noteworthy  are  the  rectal 
tracheal  gills  of  odonate  nymphs.  In 
these  insects  the  lining-  of  the  rectum 
forms  numerous  papilke  or  lamellse,  which 

contain  a  profusion  of  delicate  tracheal 
branches;  these  are  bathed  by  water 
drawn  into  the  rectum  and  then  expelled, 
at  rather  irregular  intervals.  A  similar 
rectal  respiration  occurs  also  in  ephemerid 
nymphs  and  mosquito  larvae. 

A  few  forms,  chiefly  Perlidae,  are 
exceptional  in  retaining  tracheal  gills 
in  the  adult  stage ;  in  some  imagines 
they  are  merely  vestiges  of  the  nymphal 
gills,  but  in  others,  such  as  Pteronarcys 
(Fig.  18),  which  habitually  dips  into 
the  water  and  rests  in  moist  situations, 
the  gills  probablv  supplement  the  spira- 
.i;r  <:J-,./s;:r:  cles.  Further  details  on  the  respiration 
ing     respiratory     tube.      ^f  aquatic  iusccts  are  given  in   Chapter 

Natural      size.  —  After 

Hapt.  IV. 


Caterpillar  of  Para- 
ponyx  obscuralis,  to  show 
tracheal  gills.  Length, 
15  mm. — After  Hart. 


Fig.  172. 


136 


ENTOMOLOGY 


Spiracles. — The  paired  external  openings  of  the  tracheae 
occur  on  the  sides  of  the  thorax  and  abdomen,  there  being 
never  more  than  one  pair  to  a  segment.  Though  the  thysa- 
nuran  Japy.v  has  ii  pairs,  no  winged  insect  has  more  than  lo; 
ahhough  there  are  in  all  12  segments  which  may  bear  spiracles 
— the  three  thoracic  and  the  first  nine  abdominal  segments. 
(Additional  details  are  given  on  page  66.) 

The  spiracles,  or  stigmata,  are  usually  provided  with  bris- 
tles, hairs  or  other  processes  to  exclude  dust ;  or  the  hairs  of 
the  body  may  serve  the  same  purpose,  as  in  Lepidoptera  and 
Diptera ;  in  many  beetles  the  spiracles  are  protected  by  the 
elytra ;  in  other  beetles,  however,  and  in  many  Hemiptera  and 
Diptera  the  spiracles  are  unprotected  externally.  Larvje  that 
live  in  water  or  mud  may  have  spiracles  at  the  end  of  a  long 

Fig.  173. 


Apparatus    for    closing    the    spiracular    trachea    in    a    beetle,    Luc 
opened;    B,   closed;    b,    bow;    bd,    band;    c,    external    cuticula;    /,    lever; 
spiracle;   t,  trachea. — After  Judeich   and   Nitsche. 


4,    trachea 
muscle;    s, 


tube,  which  can  be  thrust  up  into  the  pure  air;  this  is  true  of 
the  dipterous  larv?e  of  Eristalis,  Bittacouwrpha  (Fig.  172) 
and  Culcx  (Fig.  229). 

Closure  of  Spiracles. — As  a  rule,  a  spiracle  is  opened  and 
closed  periodically  by  means  of  a  valve,  operated  by  a  special 
occlusoi'  muscle.  In  dipterous  larvae  the  closure  is  effected  by 
the  contraction  of  a  circular  muscle,  but  Coleoptera  and  Lepi- 
doptera, among  other  insects,  ha\'e  a  somewhat  complex  appa- 
ratus for  closing  the  trachea  immediately  behind  the  spiracle. 


ANATOMY    AND    PIIVSIOLOGV 


137 


Tims,  in  the  stag-beetle,  a  crescentic  bo-.i'  (  I-'ig.  173,  /;)  extends 
half  around  the  trachea,  and  the  rest  of  the  circumference  is 

s])anned  hy  a  /cc'cr  (/)  and  a  band  (/></)  ;  these  three  chitinons 


ny-  around   the  trachea, 
the  lever  and  the  hand. 

Fk;.   i7i. 


])arts,  articulated  to.^ether,  form  a  r 
I'urthermorc,  a  muscle  ( /// )  connects 
As  the  muscle  shortens,  the  lexer 
turning-  ui)on  the  end  of  the  hand  as 
a  fulcrum,  pulls  the  l)o\v  toward  the 
lever  and  hand  until  the  enclosed 
trachea  is  pinched  together,  ^^dlen 
the  muscle  relaxes,  the  trachea  opens 
1)_\-  its  own  elasticity. 

Structure  of  Tracheae.  —  The 
trachea'  originate  in  the  emhrvo  as 
simple  in-pocketings  of  the  outer 
germ  layer,  or  ectoderm,  and  from 
these  the  countless  tracheal  l)ranches 
are  deri\'ed  by  the  same  process 
of  invagination.  The  lining  mem- 
brane of  a  trachea  is,  then,  con- 
tinuous   with    the    external    cuticula, 

and  the  cellular  wall  of  a  trachea  is  continuous  wdth  the 
rest  of  the  hypodermis.  This  wall  consists  of  a  layer  of 
polygonal  cells  (Fig.  174)  fitting  closely  together  as  a  paz'c- 
mcnt  epithelium.  The  chitinous  lining-,  or  iiitiiiia,  is  thick- 
ened at  regular  intervals  to  form  thread-like  ridges,  which 
course  around  the  inner  circumference  in  essentially  a  spiral 
manner,  though  the  continuity  of  the  so-called  spiral  thread  is 
frecjuently  interrupted.  These  elastic  threads,  or  tccnidia, 
serve  to  keep  the  trachea  open  without  affecting  its  flexibility. 

The  ultimate  tracheal  branches  (Fig.  175)  are  extremely 
delicate  tubes,  which  do  not  end  blindly,  but  anastomose  with 
one  another,  forming-  a  capillary  network  of  continent  tubes. 
Some  authors  have  held  that  the  finest  tracheal  filanients  pene- 
trate epithelial  or  other  cells. 

Respiration. — The   external    signs   of   respiration   are   the 


Structure  of  a  trachea.  .';, 
icheal  hypodermis;  i,  intima; 
t.-enidium. 


i^iS 


ENTOMOLOGY 


regular  opening  and  closing  movements  of  some  of  the  spira- 
cles and  the  rhythmic  contraction  and  expansion  of  the  abdo- 
men.    During  contraction,  the  dorsal  and  ventral  walls  ap- 


Tracheal   capillary   end-network    from   silk   gland   of  Porthetria   dispar.     p,    peritracheal 
membrane;    t,   tracheal   capillary. — After   Wistingh.\usen. 

proach  each  other  (Fig.  176)  and  during  expansion  they 
separate.  The  tergum  moves  more  than  the  sternum  in  Cole- 
optera  and  Heteroptera,  and  vice  ^■ersa  in  Acridiidae,  Odonata, 
Diptera  and  aculeate  Hymenoptera.  The  width  of  the  abdo- 
men usually  changes  but  little  during  respiration,  for  the  ter- 
gal and  sternal  movements  are  taken  up  by  the  pleural  mem- 

FiG.  176. 
I  t 


A  ^ 

Transverse  sections  of  abdominal  segments,  to  illustrate  respiratory  movements.  A, 
cockroach  (Blatta);  B,  bee  (Boinbiis):  s,  sternum;  t,  tergum.  The  dotted  lines 
indicate  positions  of  terga  and  sterna  after  expiration;  the  continuous  lines,  after 
inspiration. — After   Plateau. 

bra  lies  which,  as  in  the  grasshopper,  infold  at  contraction  and 
straighten  out  at  expansion.  Other  respiratory  movements 
occur,  but  they  are  of  minor  importance. 


ANATOMY    AND    PHYSIOLOGY 


139 


Tlie  rate  of  respiration  increases  or  diminishes  with  the 
activity  of  the  insect  and  with  temperature  and  other  conch- 
tions.  In  six  specimens  of  Mclanophis  diiferciitialis,  held  he- 
tween  the  fino-ers,  the  thoracic  spiracles  opened  and  closed 
resi)ectively  34.  43,  45.  54,  ()0 
indi\-i(hi.'ds     of     .1/.     fcniiir- 


riibniiii  under  the  same  cii 


()i  times  per  minute.     Four 


'O, 


90 


cumstances  g; 
and  t;2. 

At  expansion  inspiration 
takes  place,  and  at  contrac- 
tion expiration  occurs.  In 
the  grasshopper,  the  thoracic 
spiracles  open  almost  simul- 
taneously with  the  expan- 
sion of  the  ahdomen.  Con- 
traction is  effected  by  special 
vertical  expiratory  muscles 
(Fig.  177),  but  expansion 
is  due  to  the  elasticity  of 
the  abdominal  wall,  as  a 
rule ;  this  is  the  reverse 
of  what  occurs  in  mam- 
mals, wdiere  expiration  is 
passive  and  inspiration  ac- 
tive. Inspiratory  muscles 
are  found,  however,  in  Acridiida;,  Trichoptera  and  Hymen- 
optera. 

Though  the  respiratory  movements  of  an  insect  may  be 
studied  with  a  hand-lens,  a  more  precise  method  is  that  of 
Plateau — the  chief  authority  on  insect  physiology — who  made 
use  of  the  stereopticon  to  project  an  enlarged  profile  of  the 
insect  upon  a  screen,  on  which  could  be  marked  the  different 
contours  of  the  abdomen  at  its  phases  of  inspiration  and 
expiration. 

The  way  in  which  the  air  reaches  the  finest  tracheal  branches 


Diagrammatic  cross  section  of  abdomen 
of  a  grasshopper,  Acridium.  d,  dorsal 
septum,  or  diapliragm;  ex,  expiratory  mus- 
cle; /,  fat-body;  g,  ganglion;  /;,  heart;  in, 
inspiratory  muscle;  r,  ventral  septum,  be- 
low which  is  the  ventral  sinus.  The  dorsal 
and  ventral  septa  rise  and  fall  periodically. 
— After  Graber. 


I40 


ENTOMOLOGY 


is  not  clearly  ascertained,  but  it  is  thoiig-ht  that  air  is  forced 
into  these  tubes  by  pressure  from  the  abdominal  muscles,  while 
its  escape  through  the  spiracles  is  being  prevented  by  the  com- 
pression of  the  stigmatal  trache??. 

The  respiratory  movements  are  entirely  reflex  and  are  inde- 
pendent of  the  brain  or  suboesophageal  ganglion,  for  they  con- 
tinue after  decapitation  and  even  in  the  detached  abdomen  of 
a  grasshopper  or  dragon  fly.  Each  ventral  ganglion  of  the 
body  is  an  independent  respiratory  center  for  its  particular 
segment. 

lo.  Reproductive  System 

The  sexes  are  always  separate  in  insects,  hermaphroditism 
occurring  only  as  an  abnormal  condition.  The  sexual  organs, 
situated  in  the  abdomen,  consist  essentially  of  a  pair  of  ovaries 


Fig.  1/8. 


Fig.  179. 


Reproductive  system  of  male  beetle,  Melo 
lontha.  a,  accessory  gland;  c,  copulatory 
organ;  d,  ejaculatory  duct;  s,  seminal  vesicle; 
t,  testis;   v,  vas  deferens. — After  Kolbe. 


Reproductive  system  of  male 
Lepidoptera.  a,  accessory  gland; 
d,  ejaculatory  duct;  t,  vniited 
testes;  v,  vas  deferens. — After 
Kolbe. 


or  testes  and  a  pair  of  ducts  [oviducts  or  seminal  ducts,  respec- 
tively). Primitively,  the  ducts  open  separately,  as  they  still 
do  in  Ephemeridic.  but  in  nearly  all  other  insects  the  two  ducts 
enter  a  common  evacuating  duct  {vagina  or  ejaculatory  duct)  ; 
this  opens  ordinarily  between  the  penultimate  and  antepenulti- 
mate segments  of  the  abdomen,  i.  e.,  usually  the  ninth  and 
eighth,  at  any  rate  never  through  the  last  abdominal  segment. 


ANATOMY    AND    PHYSIOLOGY 


141 


Homologies. — As  in  other  animals,  the  repr(~)(hicti\c  or- 
gans are  homologous  in  the  two  sexes.     Thus : 

Male.  Fkmale. 

Testes  =  Oi'orics 
Sciniiuil  ducts  =^  Oc'idiuts 
Ejaculatory  duct  =  Vagina 

Seminal  vesicle  =  Seminal  receptacle 
Accessory  glands  =  Accessory   glands 
Penis  and  accessories  =  Ovipositor 

Male  Organs. — Each  testis,  though  sometimes  a  single 
blind  tube,  is  usually  a  group  of  tubes  or  sacs  (Fig.  178), 
testicular  follicles,  which  open  into  a  seminal  duct  (z'as  clefer- 


FiG.  180. 


Fig.  18 


Spermatozoa.  A,  locustid 
grasshopper;  B,  cockroach, 
Blatta;  C,  beetle,  Copris. 
— After    BuTSCHLi    and    Bal- 

LOWITZ. 


Reproductive  system  of  queen 
honey  bee.  a,  accessory  sac  of 
vagina;  b,  bulb  of  stinging  ap- 
paratus; c,  colleterial,  or  cement, 
gland;  o,  ovary;  od,  oviduct;  p, 
poison  glands;  pr,  poison  reser- 
voir; r,  receptaculum  seminis; 
re,  rectum;  ?■,  vagina. — After 
Leuckart. 


ens).  In  most  Lepidoptera  the  testes  are  secondarily  united 
into  a  single  mass  (Fig.  179)  as  also  in  /Vcridiidae.  The  two 
seminal  ducts  enter  the  common  ejaculatory  duct,  which  ter- 


142 


ENTOMOLOGY 


minates  in  the  intromittent  organ,  or  penis.  Often  each  vas 
deferens  is  dilated  near  its  mouth  into  a  sciiiiiiol  vesicle,  or 
reservoir;  or  there  may  be  only  a  single  seminal  vesicle,  aris- 
ing from  the  common  duct.  One  or  more  pairs  of  glands 
opening  into  the  vasa  deferentia  or  the  liiictiis  cjaciilaforiiis 
secrete  a  fluid  which  mixes  with  the  spermatozoa  and  often- 
times unites  them  into  packets,  known  as  spermatophorcs. 

All  these  parts  are  subser- 
vient to  the  formation,  pres- 
ervation and  emission  of  the 
spcnnatozoa.  These  minute 
thread-like  bodies  (Fig.  i8o) 
arise  in  the  testicular  follicles 
from  a  germinal  epitheliuni, 
and  consist,  as  in  vertebrates, 
of  a  head,  middle-piece  and 
a  vibratile  /a/7 — without  en- 
tering into  the  finer  struc- 
ture. 

Female  Organs.  —  Each 
oi'ary  (Fig.  i8i  )  consists  of 
one  or  more  tubes  opening 
into  an  oviduct.  The  two 
oviducts  enter  a  common 
duct,  the  z'agina,  which 
opens  to  the  exterior,  often 
through  an  ovipositor.  Fre- 
quently the  vagina  is  ex- 
panded as  a  pouch,  or  bursa  copulatrix,  though  in  Lepidoptera 
the  bursa  and  the  vagina  are  distinct  from  each  other  and  open 
separately  (Fig.  182).  In  most  insects  a  dorsal  evagination 
of  the  vagina  forms  a  seminal  receptacle,  or  spermatheca,  from 
which  spermatozoa  emerge  to  fertilize  the  eggs.  The  acces- 
sory glands,  either  paired  or  single,  provide  a  secretion  for 
attaching  the  eggs  to  foreign  objects,  cementing  the  eggs  to- 
gether, forming  an  egg-capsule,  etc. 


Reproductive  system  of  female  Lepi- 
doptera. b,  bursa  copulatrix;  /,  terminal 
filament;  g,  cement  glands;  o,  o,  ovaries; 
od,  oviduct;  r,  receptaculum  seminis;  -■, 
vagina;  I's,  vestibule,  or  entrance  to 
bursa. — After  Kolbe. 


ANATOMY    AND    PHYSIOLOGY 


H3 


Tn  each  ovarian  tube,  or  ovariole,  are  found  ova  in  succes- 
sive stai^-es  o\  j^rowth,  the  lars^est  and  oldest  ovum  being-  near- 
est the  o\i(hict.  In  the  ])rimitive  t}-pe  of  egg'-tube,  as  in  Thys- 
aiuu-a  and  Ortho])tera  (Fig.  183,  A)  every  chaniljer  ccjntains 
an  o\-uni ;  in  more  speciahzed 
types,  every  other  chamber  con- 
tains a  nutritive  cell  instead  of  a 
germ  cell,  the  nutriti\e  cells  serv- 
ing as  fo(_)d  ft)r  the  adjacent  o\-a 
[B)  ;  or  the  nutriti\e  cells,  in- 
stead of  alternating  with  the  ova, 
may  be  collected  in  a  special 
chamber,  Ijeyond  the  ovarian 
chambers  {C).  An  egg-tube  is 
usually  prolonged  distally  as  a 
terminal  filament,  or  suspciisor, 
the  free  end  of  which  is  attached 
near  the  dorsal  vessel. 

Ovaries  and  testes  arise  from 
indifferent  cells,  or  primitive 
germ  cells,  which  are  at  first 
exactly  alike  in  the  two  sexes. 
In  the  female,  certain  of  these 
cells  form  o\a  and  others  form  a 
foUicic  around  each  o\-um  (Fig. 
184).  In  the  male,  the  primary 
germ  cells  form  cells  termed 
spcniiafogoiiia ;  each  of  these 
forms  a  spcniiafocytc,  and  this 
gives  rise  to  four  spcriuatocoa. 

Hermaphroditism. — The  phenomenon  of  hcnnaphrodi- 
fisiii,  or  the  combination  of  male  and  female  characters  in  the 
same  individual,  occurs  only  as  an  extremely  rare  abnormality 
among  insects.  Speyer  estimated  that  in  Lepidoptera  only 
one  individual  in  thirty  thousand  is  hermaphroditic.  Bertkau 
(1889)  listed  335  hermaphroditic  arthropods,  of  which  8  were 


Types  of  ovarian  tubes.  A,  with- 
out nutritive  cells;  B,  with  alternat- 
ing nutritive  and  egg-cells;  C,  with 
terminal  nutritive  chamber;  c,  ter- 
minal chamber;  e,  egg-cell;  ep,  fol- 
licle epithelium;  f,  terminal  fila- 
ment; s,  strands  connecting  ova 
with  nutritive  chamber;  _v,  yolk,  or 
nutritive,  cells. — From  Lang's  Lclir- 
biu-h. 


144 


ENTOMOLOGY 


crustaceans.  2  spiders,  2  Orthoptera,  8  Diptera,  9  Coleoptera, 
51  Hymenoptera  and  255  Lepidoptera.  The  large  proportion 
of  Lepidoptera  is  due  in  great  measure 
to  the  fact  that  they  are  collected 
of tener  than  other  insects  ( excepting 
possil)ly  C(^leoptera )  and  that  sexual 
dimorphism  is  so  prevalent  in  the 
order  that  hermaphrodites  are  easily 
recognized. 

The  most  common  kind  of  her- 
maphroditism is  that  in  which  one 
side  is  male  and  the  other  female,  as  in 
Fig.  185.  Bertkau  found  this  right- 
and-left  hermaphroditism  in  153  in- 
dividuals. In  other  instances  the 
antero-posterior  kind  may  occur,  as 
when  the  fore  wings  are  of  one  sex 
and  the  hind  wings  of  the  other ; 
rarelv,  the  characters  of  the  two  sexes 
are  intermingled. 
Hermaphroditic  insects  are  such  rarities  that  very  few  of 
them  have  heen  sacrificed  to  the  dissecting  needle  in  order  to 

determine      whether     the 

Fig.  185. 
phenomenon  involves  the 

primary  organs  as  well  as 
the  secondary  sexual  char- 
acters. Where  dissections 
have  been  made  it  has 
been  found  usually  that 
hermaphroditism  does  ex- 
tend to  the  reproductive 
organs  themselves.  Thus 
a  butterfly  with  male 
wnngs  on  the  right  side 
and  female  wings  on  the 
left  would  have  a  testis  on  the  right  side  of  the  abdomen  and  an 
ovary  on  the  left  side. 


Ovum  of  a  butterfly,  Va- 
nessa, in  its  follicle,  e,  fol- 
licle epithelium;  g,  germinal 
vesicle;  n,  branching  nucleus 
of  nutritive  cell;  o,  ovum. — 
After   WooDWORTH. 


Hermaphrodite  gypsy  moth,  Porthetn'a  dis- 
bar; right  side,  male;  left,  female.  Natural 
size. — After  Taschenberg,  from  Hertwig's 
Lchrbiich. 


ANATOMY    AND    PHYSIOLOGY  1 45 

Parthenogenesis. — Reproduction  without  fertilization  is  a 
normal  phenomenon  in  not  a  few  insects.  This  parthcno- 
o^cncsis  may  easily  he  ohserved  in  i)lant  lice.  In  these  insects 
there  are  many  snccessixe  hroods  consistino-  of  females  only, 
which  hrino-  forth  livin,^-  yonn,^-;  at  dehnite  intervals,  however, 
and  usually  in  autumn,  males  ajjpear  also,  and  fertilized  eggs 
are  laid  which  last  o\er  winter.  This  cyclic  reproduction,  by 
the  way,  is  known  as  Jictcrogcny.  Among  Hymenoptera, 
parthenogenesis  is  prevalent,  usually  alternating  with  sexual 
reproduction,  as  in  many  Cynipidos.  In  some  Cynipidse,  how- 
ever, males  are  unknown ;  such  is  the  case  also  in  some  Ten- 
thredinidse.  The  statement  has  long  been  made  that  the  un- 
fertilized eggs  of  worker  ants,  bees  and  wasps  produce  in\ari- 
ably  males;  it  has  been  found  recently,  however,  that  the  par- 
thenogenetic  worker  eggs  of  the  ant  Lasius  nigcr  may  produce 
normal  workers  (  Reichenbach,  Mrs.  A.  B.  Comstock).  Males 
may,  of  course,  result  from  fertilized  eggs,  as  in  the  honey  bee, 
according  to  Dickel;  who  maintains,  indeed,  that  all  the  eggs 
laid  by  the  queen  bee  are  fertilized.  Parthenogenesis  has  been 
recorded  as  occurring  also  in  a  few  moths,  some  Coccidse  and 
many  Thysanoptera. 

Paedogenesis." — In   Miasfor  and   some   species   of   Cccido- 

inyia,  young  are  produced  l;)y  the  lar7'a.     This  extraordinary 

form  of  parthenogenesis  is  termed  pccdogciicsis,  and  is  limited 

Fig.  iJ 


Young   paedogenetic   larvae   of   Miastor   in   the    body   of   the   mother    larva.     Greatly   en- 
larged.— After   Pagenstkcher. 

apparently  to  the  family  Cecidomyiid^e.  The  pcedogenetic 
larvae  of  Miastor  (Fig.  i86)  develop  before  the  oviducts  have 
appeared  and  escape  by  the  rupture  of  the  mother.  After 
several  successive  generations  of  this  kind  the  resulting  larvae 
pupate  and  form  normal  male  and  female  flies.  The  pupa  of 
a  species  of  Chirononiiis  occasionally  deposits  unfertilized 
eggs,  wdiich  develop,  however,  in  the  same  manner  as  the  fer- 
tilized eggs  of  the  species. 


CHAPTER    III 


DEVELOPMENT 


I.  Embryology 
Ovum. — The  ovum  of  an  insect,  as  of  any  other  animal, 
is  a  single  cell  (Fig.  187),  with  a  large  nucleus  (genninal 
vesicle) ,  a  large  nucleolus,  nutritive  mat- 
ter, or  yolk  {dcutoplasni) ,  contained  in 
the  cytoplasm,  and  a  cell  wall  {vitelline 
niemhraue)  secreted  hy  the  ovum;  the 
egg-shell,  or  chorion,  is  secreted  around 
the  o\-um  by  surrounding  ovarian  cells. 

Maturation. — As  a  preparation  for 
fertilization  the  germinal  vesicle  divides 
twice,  forming  two  polar  bodies,  and  as 
the  first  of  these  bodies  may  itself  divide, 
there  result  iouv  cells ;  three  of  these, 
however — the  polar  bodies — are  minute 
and  rudimentary. 

These  phenomena  of  ovogenesis  are 
paralleled  in  the  development  of  the  sper- 
matozoa, or  speriuafogeuesis;  for  the  pri- 
mary spennafocyfe  gives  rise  to  two  sec- 
ondary spermatocytes,  and  these  to  four 
spermatids,  each  of  which  forms  a  sper- 
matozoon. 

By  means  of  this  maturation  process 
the  number  of  chromosomes  in  the  egg- 
nucleus  is  reduced  to  half  the  number 
normal  for  sonmtic  cells  (body  cells  as 
distinguished  from  germ  cells).  A  sim- 
ilar reduction  occurs  also  during  the  de- 
velopment of  the  spermatozoon,  and  when  sperm-nucleus  and 

146 


Sagittal  section  of  egg 
of  fly,  Musca,  in  process 
of  fertilization,  c,  cho- 
rion; d,  dorsal;  in,  mi- 
cropyle,  with  gelatinous 
exudation;  p,  male  and 
female  pronuclei,  before 
union;  pb,  polar  bodies; 
pr,  peripheral  proto- 
plasm; r,  ventral;  vt, 
vitelline  membrane;  y, 
yolk.  —  After  Henking 
and   Blochmann. 


DEVELOPMENT  147 

cgg-iiuc!cus  unite,  the  resulting-  nucleus  contains  the  normal 
number  of  chromosomes.  The  meaning-  of  these  reduction 
phenomena — highly  important  from  the  standpoint  of  heredity 
— is  a  much  debated  subject. 

Fertilization. — As  the  eggs  pass  through  the  vagina,  they 
are  capable  of  being  fertilized  by  spermatozoa,  previously 
stored  in  the  seminal  receptacle.  Through  the  inicropylc  of 
the  chorion  one  or  more  spermatozoa  enter  and  a  sperm- 
nucleus  unites  with  the  eg-g-nucleus  to  form  what  is  known  as 
the   segiiirnfafioti    mtclriis.     Through   this    union    of   nuclear 

Fig.  1 88. 


Equatorial    section    of    egg    of    a    beetle.    Clytra    Itriiiisciila.      b.    blastoderm;    g,    germ 
band;   y,   yolk   granule;   yc,   yolk  cell. — After  Lecaillon. 

substances  the  qualities  of  the  two  parents  are  combined  in  the 
offspring-.  Needless  to  say.  the  minute  details  of  the  process 
of  fertilization  are  of  the  highest  biological  importance. 

Blastoderm. — In  an  arthropod  ovum  the  yolk  occupies  a 
central  position  {ccntrolccithal  type),  being  enclosed  in  a  thin 
layer  of  protoplasm.  From  the  segmentation  nucleus  just 
mentioned  are  derived  many  nuclei,  some  of  which  migrate 
outward  with  their  attendant  protoplasm  to  form  with  the 
original  peripheral  protoplasm  a  continuous  cellular  layer,  the 
blastoderm  (Fig.  i88). 


148 


ENTOMOLOGY 


Germ  Band. — The  blastoderm,  at  first  of  uniform  thick- 
ness, becomes  thicker  in  one  region,  by  cell  multiplication, 
forming  the  genu  baud  {primitive  streak,  etc.)  ;  this  appears 
in  surface  view  as  an  o^'al  or  elongate  area,  denser  than  the 
remaining  blastoderm,  with  which  it  is,  of  course,  continuous. 

Fig.  1 89. 


»^£fe 


.  ransverse   sectic 


of   germ   band    of    Clytra    at   gastrulation. 
layer. — After    Lecaillon. 


g,    germ    band; 


Gastrulation. — The  germ  band  next  infolds  along  the  me- 
dian line,  appearing  in  cross  section,  as  in  Fig.  189;  the 
two  lips  of  the  median  groove  close  together  over  the  inva- 
ginated  portion  and  form  an  outer  layer,  or  ectoderm  (Fig. 
igo),  while  the  invaginated  portion  spreads  out  as  an  inner 


Fig.  190 


Transverse  section  of  germ  layers 
and  amnion  folds  of  Clytra.  a,  am- 
nion; e,  ectoderm;  i,  inner  layer 
(meso-entoderm) :  5,  serosa. — Original, 
based   on   Lecaillon's   figures. 


Transverse  section  of  germ  layers  and 
embryonal  membranes  of  Clytra.  a,  am- 
nion; ac,  amnion  cavity;  e,  ectoderm;  i, 
inner  layer  (meso-entoderm)  ;  s,  serosa. 
— After   Lecaillon. 


layer,  which  is  destined  to  form  two  layers,  known  respectively 
as  entoderm  and  mesoderm.     This  formation  of  two  primary 


tioii;  it  is  an  important  stage  in  the  development  of  all  eggs, 
and  among  insects  several  variations  of  the  process  occur. 
Amnion  and  Serosa. — ^Meanwhile,  the  blastoderm  has  been 


DEVELOPMENT 


149 


folding  over  tlie  germ  band  from  either  side,  as  shown  in  Fig. 
190,  and  at  length  the  two' folds  meet  and  unite  to  form  two 
membranes  (Fig.  191).  namely,  an  inner  one,  or  amnio)!,  and 
an  outer  one,  or  serosa. 

Fig.  192. 

.:^;?^^^.  „.  •-'''.:■■":  ''h.. 


lif' 


WM 


Germ  band  of  a  beetle,  Mdasoina. 
B,  with  oral  segments  demarkated :  C 
dominal   segments. — After   Grablr. 


three    successive    stages.     A,    unsegmented; 
th    three    oral,    three    thoracic    and    two    ab- 


Segmentation  and  Appendages. — On  the  germ  band, 
which  represents  the  ventral  part  of  the  future  insect,  the  body 
segments  are  marked  off  by 
transverse  grooves  (Figs. 
192,  194)  ;  this  segmentation 
beginning  usually  at  the  an- 
terior end  of  the  germ  band 
and  progressing  backward. 
Furthermore,  an  anterior  in- 
folding occurs  (Fig.  193), 
forming  the  stoiiiodcruni, 
from  which  the  mouth, 
pharynx,  oesophagus  and  other  parts  of  the  fore  gut  are  to 
arise;  a  similar,  but  posterior   invagination,  or  proctodeum 


s  '  ^  g 

Diagrammatic  sagittal  section  of 
hymenopterous  egg  to  show  stomodaeal 
is)  and  proctodaeal  (/>)  invaginations 
of   the   germ   band    {g). — .\fter   Graber. 


150  ENTOMOLOGY 

(Fig\  193),  is  the  beginning,  or  fuudauicut,  of  the  hind  gut. 
At  the  anterior  end  of  the  germ  band  is  a  pair  of  large 
proccphalic  lobes  (Figs.  192,  194).  which  eventuahy  bear  the 
lateral  eyes,  and  immediately  behind  these  are  the  fundaments 
of  the  antenncT.     The  fundaments  of  the  primary  paired  ap- 
pendages are  out-pocketings  of  the  ecto- 
iG.  194.  dermal  germ  band,  and  at  first  antennae, 

C"^''^^  month  parts  and  legs  are  all  alike,  except 

N^         i  in    their   relative   positions.     Behind   the 

a.._  y->r *-3y- i  antennae    (in  Thysanura  and  Collembola 

.O-I-IOl—  '"  at  least)   appears  a  pair  of  rudimentary 

■"  '"^       appendages     (Fig.     194,    ;")     which    are 
"      -        thought  to  represent  the  second  antennae 
•  2  of  Crustacea ;  instead  of  developing,  they 

yO.-4X4--t-— f^        disappear  in  the  embryo  or  else  persist  in 
^;jlJJj?^;— a^  the  adult  as  mere  rudiments.     In  front  of 

-'^Hf'^'       ^  these  transitory  intercalary  appendages  is 

-^f^" "  ^  the     mouth-opening,     above     which     the 

31-^^       '^         labrum  and  clypeus  are  already  indicated 
-.^.?    2ll  "  ^"^  ^^y  '^  single,  median  evagination.      Behind 

'^-....  pf.  the   mouth    the   mandibles,    maxillae    and 

labium  are  represented  by  three  pairs  of 

\'entral   aspect  of  germ 

band  of  a  coiiemboian,  fuudameuts,  and  iu  Thysanura  and  Col- 
t:™:, . :XaMLi„:,  >embola  a  fourth  pa,r  is  present  to  form 
appendages;  i,  intercalary     the  superliuguje  (Fig.  195,  sl) ,  alrcadv  rc- 

appendage;    /,   labrum;    li,         ^  . 

left  labial  appendage;  fcrred  to.  A cxt  lu  ordcr  are  the  three 
"n    "l""'^'^'"'  /"■!''  ,T'     pairs  of  thoracic  legs  (Fig.  194)  and  then, 

illa;   p,   procephalic    lobe:        "^  o      \        o        ^^ / 

pr,    proctodaeum;    t^-t^     in  many  cascs,  paired  abdominal  appen- 

thoracic   legs.  ,  ,„.  ^  .         .          . 

dages  (rigs.  194,  196),  indicating  an 
ancestral  myriopod-like  condition ;  some  of  these  abdominal 
limbs  disappear  in  the  embryo  but  others  develop  into  abdomi- 
nal prolegs  (Lepidoptera  and  Tenthredinidae),  external  genital 
organs  (Orthoptera,  Hymenoptera.  etc.)  or  other  structures. 
The  study  of  these  embryonic  fundaments  sheds  much  light 
upon  the  morpholog}^  of  the  appendages  and  the  subject  of 
segmentation. 


DEVELOPMENT  I  51 

Two  Types  of  Germ  Bands. — The  g-erm  l^and  described 
above  belongs  to  the  simple  oz'crgroii'ii  type,  exemplified  in 
Clytra,  in  which  the  germ  band  retains  its  original  posi- 
tion and  the  amnion  and  serosa  arise  by  a  process  of  over- 
growth (Figs.  190,  191),  as  distinguished  from  the  invaginated 
type,  illustrated  in  Odonata,  in  which  the  germ  band  inva- 
ginates  into  the  egg,  as  in  Fig.  197,  until  the  ventral  surface 


Anterior  aspect  of  embryonal  mouth  parts  of  a  collembolan,  Anurida  maritima.  a, 
antenna;  /,  labrum;  Ig,  prothoracic  leg;  li,  left  fundament  of  labium;  In,  lingua;  m, 
mandible;    in.r,   maxilla;  p,  maxillary  palpus;   si,   superlingua. — After   Folsom. 

of  the  embryo  becomes  turned  around  and  faces  the  dorsal  side 
of  the  egg.  In  this  event,  a  subsequent  process  of  revolution 
occurs,  by  means  of  which  the  ventral  surface  of  the  embryo 
resumes  its  original  position  (Fig.  198). 

Dorsal  Closure. — As  was  said,  the  germ  band  forms  the 
ventral  part  of  the  insect.  To  complete  the  general  form  of 
the  body  the  margins  of  the  germ  band  extend  outward  and 
upward  (Fig.  199)  until  they  finally  close  over  to  form  the 
dorsal  wall  of  the  insect.  Besides  this  simple  method,  how- 
ever, there  are  several  other  ways  in  which  the  dorsal  closure 
may  be  effected. 

Nervous  System. — Soon  after  gastrulation.  the  ventral  ner- 
vous system  arises  as  a  pair  of  parallel  cords  from  cells  (Fig. 


ENTOMOLOGY 


Fig.  196. 


200,  ;/)  which  have  been  derived  by  direct  prohferation  from 
those  of  the  germ  band,  and  are  therefore  ectodermal  in  origin. 
This  primitive  double  nerve  cord  l^ecomes  constricted  at  inter- 
vals into  segments,  or  iicuromercs,  which  correspond  to  the 
segments  of  the  germ  band.  Each  nenromere  consists  of  a 
pair  of  primitive  ganglia,  and  these 
are  connected  together  by  paired 
nerve  cords,  which  later  may  or 
may  not  unite  into  single  cords ; 
moreover,  some  of  the  ganglia 
finally  unite  to  form  compound 
ganglia,  such  as  the  brain  and  the 
subcesophageal  ganglion.  In  front 
of  the  oesophagus  (Fig.  55)  are 
three  neuromeres  :  ( i )  pvotoccrc- 
bnuii,  which  is  to  bear  the  com- 
pound eyes ;  (2)  deutoccrcbniui,  or 
antennal  neuromere  ;  ( 3  )  trifoccrc- 
bruui,  which  belongs  to  the  seg- 
ment which  bears  the  rudimentary 
intercalary  appendages  spoken  of 
above.  Behind  the  oesophagus  are, 
at  most,  four  neuromeres,  namely 
and  in  order,  mandihnlar,  siipcr- 
liiigual  (found  only  in  Collembola 
as  yet),  maxillary  and  labial. 
Then  follow  the  three  thoracic  gan- 
glia and  ten  (usually)  abdominal 
ganglia.  The  first  three  neuro- 
meres always  unite  together  to 
form  the  brain,  and  the  next  four 
( always  three ;  but  four  in  Col- 
lembola and  perhaps  other  insects),  to  form  the  subceso- 
phageal ganglion.  Compound  ganglia  are  frequently  formed 
also  in  the  thorax  and  abdomen  by  the  union   of  primitive 


Embryo  of  CEcanthus,  ventral 
aspect.  a,  antenna;  a>-a^,  ab- 
dominal appendages;  e,  end  of 
abdomen;  /,  labrum;  //,  left 
fundament  of  labium;  Ip,  labial 
palpus;  t^-P,  thoracic  legs;  m, 
mandible;  mp,  maxillary  palpus; 
mx,  maxilla;  p,  procephalic  lobe; 
pr,    proctodaeum. — After   Ayers. 


DEVELOPMENT 


153 


Tracheae. — The  trachea?  l)ej;-in  as  paired  invaginations  of 
the  ectoderm  {V\g.  201.  /)  ;  these  simple  pockets  elongate  and 


Diagrammatic  sagittal  sections  to  illustrate  invagination  of  germ  band  in  Calop- 
tcryx.  a,  anterior  pole;  ac,  amnion  cavity;  am,  amnion;  b,  blastoderm;  d,  dorsal; 
g,  germ  band;  h,  head  end  of  germ  band;  p,  posterior  pole;  s,  serosa;  v,  ventral;  y, 
yolk. — After  Brandt. 

Fig'.  198. 


Diagrammatic  sagittal  sections  to  illustrate  revolution  of  Caloptcryx 
antenna;  am,  amnion;  /,  labium;  l^-P,  thoracic  legs;  m,  mandible;  mx, 
serosa. — After    Br.\ndt. 


;mbryo. 
maxilla; 


154 


ENTOMOLOGY 


unite  to  form  the  main  lateral  trunks,  from  which  arise  the 
countless  branches  of  the  tracheal  system. 

Mesoderm. — From  the  inner  layer  which  was  derived 
from  the  germ  band  by  gastrulation  (Figs.  189-191)  are 
formed  the  important  germ  layers  known  as  mesoderm  and  01- 

FiG.  199. 


Diagrammatic  transverse  sections  to  illustrate  formation  of  dorsal  wall  in  a  beetle, 
Lcptinofarsa.  a,  amnion  (breaking  up  in  C);  g,  germ  band;  s,  serosa. — After 
Wheeler,    from   the   Journal  of  Morphology. 

todcrm.  Most  of  the  layer  becomes  mesoderm,  and  this  splits 
on  either  side  into  chambers,  or  ca:lom  sacs  (Fig.  200,  c) ,  a  pair 
to  each  segment.  In  Orthoptera  these  coelom  sacs  are  large 
and  extend  into  the  embryonic  appendages,  but  in  Coleoptera, 
Lepidoptera  and   Hymenoptera  they  are  small.     These   sacs 

Fig.  200. 


Tan-sverse  section  of  germ  layers  of  Clytra.     c,  ccelom  sac;  n, 
neuroblasts    (primitive    nervous  cells). — After  Lecaillon. 

may  share  in  the  formation  of  the  definite  body-cavity,  though 
the  last  arises  independently,  from  spaces  that  form  between 
the  yolk  and  the  mesodermal  tissues.  From  the  coelom  sacs 
develop  the  muscles,  fat-body,  dorsal  vessel,  blood  corpuscles, 
ovaries  and  testes ;  the  external  sexual  organs,  however,  as 
well  as  the  vagina  and  ejaculatory  duct,  are  ectodermal  in 
orig-in. 


DEVELOPMENT 


155 


Entoderm. — At  its  anterior  and  posterior  ends,  the  inner 
layer  just  referred  to  ^ives  rise  to  a  mass  of  cells  which  are 

Fig.  201. 


Transverse  section  of  abdomen  of  Clytra  embryo  at  an  advanced  stage  of  develop- 
ment, a,  appendage;  e,  epithelium  of  mid  intestine;  g,  ganglion;  m,  Malpighian  tube; 
mi,  muscular  layer  of  mid  intestine;  ms,  muscle  elements;  my,  mesenchyme  (source 
of   fat-body);   s,   sexual  organ;   t,  tracheal  invagination. — After   Lec-mllon. 


Fig.  202. 


destined  to  form  the  mcscntcron,  from  which  the  mid  intestine 

develops.     One  mass  is  adjacent  to  the  blind  end  of  the  stomo- 

d;eal  im-agination  and  the  other  to  that  of 

the     proctodajal     in-folding.     The     two 

masses  become  U-shaped  (Fig.  202),  and 

the  lateral  arms  of  the  two  elongate  and 

join  so  that  the  entodermal  masses  become 

connected  by  two  lateral  strands  of  cells : 

by   overgrowth    and    undergrowth    from 

these    lateral    strands    a    tube    is    formed 

which  is  destined  to  Ijecome  the  stomach, 

and  by  the  disappearance  of  the  partitions 

that   separate   the   mesenteron    from   the 

stomodseum  at  one  end  and  from  the  proc- 

todseum  at  the  other  end.  the  continuity 

of    the    alimentary    canal    is    established. 

The    fore    and    the   hind   gut.    then,    are 

ectodermal   in    origin,   and   the   mid   gut 

entodermal. 


formation 
of  entoderm  in  Leptino- 
tarsa.  e,  e,  entodermal 
masses;  m,  mesoderm. — 
After   Wheeler. 


156 


ENTOMOLOGY 


2.  External  Metamorphosis 
Metamorphosis. — One  of  the  most  striking  phenomena  of 
insect  Hfe  is  expressed  by  the  term  inctamorphosis,  which 
means  conspicuous  change  of  form  after  birth.  The  tgg  of 
a  butterfly  produces  a  larva;  tliis  eats  and  grows  and  at  length 
becomes  a  pupa;  Avhich,  in  turn,  develops  into  an  imago. 
These  stages  are  so  different   (Fig.  27)   that  witliout  experi- 

FiG.  203. 


Cyllcne   pi. 


A,   larva;   B,   pnpa;    C, 


ence  one  could  not  know  that  they  pertained  to  the  same 
individual. 

Holometabola. — The  more  specialized  insects,  namely, 
Neuroptera.  Alecoptera.  Trichoptera,  Lepidoptera,  Coleoptera 
(Fig.  203),  Diptera  (Figs.  204,  29),  Siphonaptera  (Fig.  30) 
and  Hymenoptera  (Fig.  280),  undergo  this  indirect,  or  com- 
plete,^ metamorphosis,  involving  profound  changes  of  form 
and  distinguished  by  an  inactive  pupal  stage.  These  insects 
are  grouped  together  as  Holometabola. 

Larvae  receive  such  popular  names  as  "'  caterpillar  "  (Lepi- 

^  These  terms,  though  somewhat  misleading  in  impHcation,  are  cur- 
rently used. 


DEVELOPMENT 


157 


doptera),  "  stuI)  "  (Coleoptera ),  and  "  maj^got  "  (Diptera), 
while  the  ]wpa  of  a  moth  or  l)ullerlly  (especiahy  the  latter) 
is  called  a  "  chrysalis." 

Heterometabola, — In  a  o-rassh()])per,  as  contrasted  with  a 
hnttertlv,  the  imago,  or  adult,  is  essentially  like  the  young  at 
birth,  except  in  having  wings  and  mature  reproductive  organs, 
and  the  insect  is  active  throughout  life;  hence  the  metamor- 
phosis is  termed  direct,  or  iiicoinplclr.     This  type  of  trans- 


Phormia  rcgiua.     A,  larva;  B 


formation,  without  a  true  pupal  period,  is  characteristic  of 
the  more  generalized  of  the  metamorphic  insects,  namely, 
Orthoptera,  Platyptera,  Plecoptera,  Ephemerida  (Fig.  19), 
Odonata  (Fig.  20),  Thysanoptera  and  Hemiptera  (Fig.  205). 
These  orders  constitute  the  group  Heterometabola.  ^^'ithin 
the  limits  of  the  group,  however,  various  degrees  of  meta- 
morphosis occur ;  thus  Plecoptera,  Ephemerida  and  Odonata 
undergo  considerable  change  of  form ;  a  resting,  or  cpiiescent, 
period  may  precede  the  imaginal   stage,  as  in   Cieada    (Fig. 


158 


ENTOMOLOGY 


206)  ;  while  male  Coccidc-e  have  what  is  essentially  a  complete 
metamorphosis.     In  fact,  the  various  kinds  of  metamorphosis 


Fig.  20= 


Six  successive  instars  of  the  squash  bug,  Anasa  tristis.     x  2. 


Fig.  206. 


Cicada    tibiccn.     A,    imago    emerging    from    nymphal    skin;    B,    the    cast    ski 
C,  imago.     Natural  size. 


grade  into  one  another  in  such  a  way  as  to  make  their  classifi- 
cation to  some  extent  arbitrary  and  inadequate. 


DEVELOPMENT 


159 


As  there  is  no  distinction  ])etween  larva  and  pnpa  in  most 
heterometabolous  insects,  it  is  customary  to  use  the  term 
n\inph  durins;-  the  interval  between  egg-  and  inia.^o. 

Ametabola. — The  most  generalized  insects,  Thysanura  and 
Collembola,  develop  to  sexual  maturity  without  a  metamor- 
phosis ;  the  form  at  hatching  is  retained  essentially  throughout 
life,  there  are  no  traces  of  wings  even  in  the  embryo,  and  there 
is  no  change  of  habit.  These  two  orders  form  the  group 
Ametabola.  All  other  insects  have  a  metamorphosis  in  the 
broad  sense  of  the  term,  and  are  therefore  spoken  of  as  Mctab- 
ola.  In  this  we  follow  Packard,  rather  than  Brauer,  who 
uses  a  somewhat  different  set  of  terms  to  express  the  same 
ideas. 

Stadium  and  Instar. — During  the  growth  of  every  insect, 
the  skin  is  shed  periodically,  and  with  each  moult,  or  ecdysis, 
the  appearance  of  the  insect  changes  more  or  less.  The  inter- 
vals between  the  moults  are  termed  stages,  or  stadia.  To 
designate  the  insect  at  any  particular  stag'e,  the  term  instar 
has  been  proposed  and  is  growing  in  favor ;  thus  the  insect  at 
hatching  is  the  first  instar,  after  the  first  moult  the  seeond 
instar,  and  so  on. 

Egg. — The  eggs  of  insects  are  exceedingly  diverse  in  form. 
Commonly  they  are  more  or  less  spherical,  oval,  or  elongate, 
but  there  are  innumerable  special  forms,  some  of  which  are 


Eggs  of  various  insects.  A,  butterfly,  Polygonia  intcrrogationis;  B,  house  fly, 
Miisca  domestica;  C,  chalcid,  Bruchophagus  funebris;  D,  butterfly,  Papilio  troiliis;  E, 
midge,  Cecidomyia  trifolii;  F,  hemipteron,  Trifhleps  insidiosus;  G,  hemipteron, 
Podisiis  spinosus;  H,   fly,    Drosophila   ampelophila.     Greatly    magnified. 


[6o 


ENTOMOLOGY 


quite  fantastic, 
in    Fig.    207. 


Fig.  208. 


Three  eggs  of  the  1 
rap<T.  Greatly  magnified 
scale. 


Something  of  the  variety  of  form  is  shown 
As  regards  size,  most  insect  eggs  can  be 
distinguished  by  the 
naked  eye ;  many  of 
them  tax  the  vision, 
however,  for  example. 
the  ehiptical  eggs  of 
Cccidoiiiyia  Icgiiiiiiiii- 
cola,  which  are  but 
.300  mm.  in  length 
and  .075  mm.  in 
width ;  the  oval  eggs 
of    the    cccropia    moth, 


ihbage     butterfly,     Pieris 
but    all    drawn    to    same 


Fig.  209. 


on  the  other  hand,  are  as  long  as  3  mm. 

The  egg-shell,  or  cJiorioii,  secreted 
around  the  ovum  by  cells  of  the  ovarian 
follicle,  may  be  smooth  but  is  usually 
sculptured,  frequently  with  ridges 
which,  as  in  lepidopterous  eggs,  may 
serve  to  strengthen  the  shell.  The 
ornamentation  of  the  egg-shell  is  often 
exquisitely  beautiful,  though  the  par- 
ticular patterns  displayed  are  probably 
of  no  use,  being  incidentally  produced 
as  impressions  from  the  cells  which 
secrete  the  chorion.  Variations  of 
form,  size  and  pattern  are  frequent  in 
eggs  of  the  same  species,  as  appears  in 
Fig.  208. 

Always  the  chorion  is  penetrated  by 
one  or  more  openings,  constituting-  the 
micro pylc,  for  the  entrance  of  sperma- 
tozoa. 

As  a  rule,  the  eggs  when  laid  are  accompanied  by  a  fluid  of 
some  sort,  which  is  secreted  usually  by  a  cement  gland  or 
glands,  opening  into  the  vagina.     This  fluid  commonly  serves 


Chrysopa.     laying     eggs. 
Slightly   enlarged. 


DEVELOPMENT  l6l 

to  fasten  the  eg-gs  to  appropriate  objects,  such  as  food  plants, 
the  skin  of  other  insects,  the  hairs  of  mammals,  etc. ;  it  may 
form  a  pedicel,  or  stalk,  for  the  egg.  as  in  Chrysopa  (  h'ig. 
209)  ;  may  surrountl  the  eggs  as  a  gelatinous  envelope,  as  in 
caddis  Hies,  dragon  tlies.  etc. ;  or  may  form  a  capsule  enclosing 
the  eggs,  as  in  the  cockroach. 

The  number  of  eggs  laid  by  one  female  differs  greatly  in 
different  species  and  varies  considerably  in  different  individ- 
uals of  the  same  species.  Some  of  the  fossorial  wasps  and 
bees  lay  only  a  dozen  or  so  and  some  grasshoppers  two  or  three 
dozen,  while  a  (jueen  honey  bee  may  lay  a  million.  Two 
females  of  the  beetle  Friomis  laticollis  had,  respectively,  332 
and  597  eggs  in  the  abdomen  (Mann).  A.  A.  Girault  gives 
the  following  numbers  of  eggs  per  female,  from  an  examina- 
tion of  twenty  egg-masses  of  each  species : 

Maximum.  Minimum.  Average. 

Thyridoptcryx  cplicmcrafoniiis      1076                753  941 

Clisiocampa    aiiicricaiia                      466                313  375-5 

Chionaspis  ftirfura                                84                  ^^  66.5 

Hatching. — Many  larv?e,  caterpillars  for  example,  simply 
eat  their  way  out  of  the  egg-shell.  Some  maggots  rupture 
the  shell  by  contortions  of  the  body.  Some  larvae  have  spe- 
cial organs  for  opening  the  shell ;  thus  the  grub  of  the  Colo- 
rado potato  beetle  has  three  pairs  of  hatching  spines  on  its 
body  (Wheeler)  and  the  larval  tiea  has  on  its  head  a  tempo- 
rary knife-like  egg-opener  (Packard).  The  process  of  hatch- 
ing varies  greatly  according  to  the  species,  but  has  received 
\ery  little  attention. 

Larva. — Although  larvae,  generally  speaking,  differ  from 
one  another  much  less  than  their  imagines  do.  they  are  easily 
referable  to  their  orders  and  usually  present  specific  dift'er- 
ences.  Larvae  that  display  individual  adaptive  characters  of 
a  positive  kind  (Lepidoptera,  for  example)  are  easy  to  place, 
but  larvae  with  negative  adaptive  characters  (many  Diptera 
and  Hymenoptera)  are  often  hard  to  identify. 
1 2 


i6; 


ENTOMOLOGY 


Thysanuriform  Larvae. — Two  types  of  larvae  are  recog- 
nized by  Braiier,  Packard  and  other  authorities:  fhysanuri- 
fonn  and  cntcifonii;  respectively  generahzed  and  speciahzed 
in  their  organization.  The  former  term  is  apphed  to  many 
larvae  and  nymphs  (Fig.  210,  C,  D)  on  account  of  their  resem- 
blance to  Thysanura,  of  which  Cauipodea  and  Lepisma  are 

Fig.  210. 


Types  of  larvK.  A,  B,  Thysanura;  C,  D,  thysanuriform  nymphs;  E-I,  cruciform 
larvae.  A,  Campodea;  B,  Lepisma;  C,  perlid  nymph  (Plecoptera) ;  D,  Libellula 
(Odonata) ;  E,  Tenthrcdopsis  (Hymenoptera) :  F,  Lachnosterna  (Coleoptera) ;  G, 
Melanotus   (Coleoptera);   H,  Boinbus    (Hymenoptera);   /,   Hypoderma    (Diptera). 

types.  The  resemblance  lies  chiefly  in  the  flattened  form,  hard 
plates,  long  legs  and  antennae,  caudal  cerci,  well-developed  man- 
dibulate  mouth  parts,  and  active  habits,  with  the  accompanying 
sensory  specializations.  These  characteristics  are  permanent 
in  Thysanura,  but  only  temporary  in  metamorphic  insects,  and 
their  occurrence  in  the  latter  forms  may  properly  be  taken  to 
indicate  that  these  insects  have  been  derived  from  ancestors 
which  were  much  like  Thysanura. 

Thysanuriform  characters  are  most  pronounced  in  nymphs 
of  Blattidae,  Forficulidae,  Perlidae,  Ephemeridae  and  Odonata, 
but  occur  also  in  the  larvae  of  some  Neuroptera  (Mantispa) 
and  Coleoptera  (Carabidae  and  Meloidae).  These  primitive 
characters  are  gradually  overpowered,  in  the  course  of  larval 
evolution,  by  secondary,  or  adaptive,  features. 


DEVELOPMENT 


163 


Eruciform  Larvae. — The  prevalent  type  of  lar\a  among 
holometabolous  insects  is  tlie  cruciform  (Fig.  210,  £-/),  illus- 
trated by  a  cater])illar  or  a  maggot.  Here  the  body  is  cylin- 
drical and  often  lleshy ;  the  integument  weak;  the  legs,  anten- 
^a^  cerci,  and  mouth  parts  reduced,  often  to  disappearance; 
the  habits  sedentary  and  the  sense  organs  correspondingly  re- 
duced. These  characteristics  are  interpreted  as  being  results  of 
partial  or  entire  disuse,  the  amount  of  reduction  being  propor- 
tional to  the  degree  of  inactivity.  Extreme  reduction  is  seen 
in  the  maggots  of  parasitic  and  such  other  Diptera  as,  secur- 
ing their  food  with  almost  no  exertion,  are  simple  in  form, 
thin-skinned,  legless,  with  only  a  mere  vestige  of  a  head  and 
with  sensory  powers  of  but  the  simplest  kind. 

Transitional  Forms. — The  eruciform  is  clearly  derived 
from  the  thysanuriform  type,  as  Brauer  and  Packard  have 
shown,  the  continuity  between  the  two  types  being  established 
by  means  of  a  complete  series  of  intermediate  stages.     The 


Fig.  211 


Mantispa.  A,  larva  at  hatching — thysanuriform;  B,  same  larva  just  before  first 
moult — now  becoming  enicifonn.  C,  imago,  the  wings  omitted;  D,  winged  imago, 
slightly  enlarged.—^  and  B  after  Br.'vuer;  C  and  D  after  Emerton,  from  Packard's 
Text-Book  of  Entomology,  by  permission  of  the  Macmillan  Co. 


beginning  of  the  eruciform  type  is  found  in  Neuroptera,  where 
the  campodeoid  sialid  larva  assumes  a  quiescent  pupal  condi- 
tion.    The  key  to  the  origin  of  the  complete  metamorphosis, 


164  ENTOMOLOGY 

involving  the  ernciform  condition,  Packard  finds  in  the  neu- 
ropterons  genus  Mantispa  (Fig.  211),  the  first  larva  of  which 
is  truly  campodea-form  and  active.  Beginning  a  sedentary 
life,  however,  in.  the  egg-sac  of  a  spider,  it  loses  the  use  of  its 
legs  and  the  antenn?e  become  partly  aborted,  before  the  first 
moult.  In  Packard's  words,  "  Owing  to  this  change  of  hab- 
its and  surroundings  from  those  of  its  active  ancestors,  it 
changes  its  form,  and  the  fully  grown  larva  becomes  cylin- 
drical, with  small  slender  legs,  and,  owing  to  the  partial  disuse 
of  its  jaws,  acquires  a  small,  round  head."  Meloiclje  (Fig. 
217)  afiford  other  excellent  examples  of  the  transition  from 
the  thysanuriform  to  the  cruciform  condition  during-  the  life 
of  the  individual. 

Thysanuriform  characters  become  gradually  suppressed  in 
favor  of  the  cruciform,  until,  in  most  of  the  highly  developed 
orders  (Mecoptera,  Trichoptera,  Lepidoptera,  Diptera,  Si- 
phonaptera  and  Hymenoptera) ,  they  cease  to  appear,  except 
for  a  few  embryonic  traces — an  illustration  of  the  principle  of 
"  acceleration  in  development." 

Growth. — The  larval  period  is  pre-eminently  one  of  growth. 
In  Heterometabola,  growth  is  continuous  during-  the  nymphal 
stage,  but  in  Holometabola  this  important  function  becomes 
relegated  to  the  larval  stage,  and  pupal  development  takes 
place  at  the  expense  of  a  reserve  supply  of  food  accumulated 
by  the  larva. 

The  rapidity  of  larval  growth  is  remarkaljle.  Trouvelot 
found  that  the  caterpillar  of  Tclca  polyphcmus  attains  in  56 
days  4,140  times  its  original  weight  (1/20  grain),  and  has 
eaten  an  amount  of  food  86,000  times  its  primitive  weight. 
Other  larvc-e  exceed  even  these  figures ;  thus  the  maggot  of  a 
common  flesh  fly  attains  200  times  its  original  weight  in  24 
hours. 

Ecdysis. — The  exoskeleton,  unfitted  for  accommodating 
itself  to  the  growth  of  the  insect,  is  periodically  shed,  and 
along  with  it  go  not  only  such  integumentary  structures  as 
hairs  and  scales,  but  also  the  chitinous  lining,  or  intima,  of 


DEVELOPMENT  165 

the  stom(Hl;cuin.  ])n)ct()(Ia'iini,  trachce,  inteoiimentary  siands, 
etc.  The  process  of  nioiiltiiii;-,  or  ccdysis,  in  caterpillars  is 
briefly  as  follows.  The  old  skin  becomes  detached  from  tlie 
body  l)y  an  interveninj^-  fluid  of  hypodermal  orio-in;  the  skin 
dries,  shrinks,  is  ])nshed  backward  by  the  contractions  of  the 
larva,  and  at  lenoth  splits  near  the  head,  frequently  under  the 
neck ;,  tln-oui^li  this  split  appear  the  new  head  and  thorax,  and 
the  old  skin  is  worked  back  toward  the  tail  until  the  larva  is 
freed  of  its  cwirz'icc.  The  details  of  tlie  process,  however,  are 
by  no  means  simple.  Ecdysis  is  probably  something-  besides 
a  pro\-ision  for  growth,  for  Collembola  continue  to  moult  long 
after  growth  has  ceased,  and  the  winged  May  fly  sheds  its 
skin  once  after  emergence.  The  meaning  of  this  is  not 
known,  though  perhaps  ecdysis  has  an  excretory  importance 
in  the  case  of  Collembola,  which  are  exceptional  among  in- 
sects in  ha\ing  no  Malpighian  tubes. 

Number  of  Moults.— The  frequency  of  moulting  differs 
greatly  in  different  orders  of  insects.  Acridiidre  ha\-e  five 
moults;  Lepidoptera  usually  four  or  five,  but  often  more,  as 
in  Isia  (Pyrrharctia)  Isabella,  which  moults  as  many  as  ten 
times  (Dyar)  ;  Musca  doniestica  has  three  (Packard);  the 
honey  bee  probably  six  (Cheshire)  ;  and  the^seventeen-year 
locust  about  twenty-five  or  thirty  (Riley).  Packard  suggests 
that  cold  and  lack  of  food  during  hibernation  in  arctians  (as 
/.  isabdla )  and  partial  starvation  in  the  case  of  some  beetles, 
cause  a  great  number  of  moults  by  preventing  grow^th,  the 
hypodermis  cells  meanwhile  retaining  their  activity. 

The  appearance  of  the  insect  often  changes  greatly  with 
each  moult,  particularly  in  caterpillars,  in  which  the  changes 
of  coloration  and  armature  may  have  some  phylogenetic  sig- 
nificance, as  Weismann  has  attempted  to  show  in  the  case  of 
sphingid  larvae. 

Adaptations  of  Larvae. — Larva;  exhibit  innumerable  con- 
formities of  structure  to  environment.  The  greatest  variety 
of  adaptive  structures  occurs  in  the  most  active  larva?,  such  as 
predaceous   forms,   terrestrial   or  aquatic.     These   have  well- 


1 66  ENTOMOLOGY 

developed  sense  organs,  excellent  powers  of  locomotion,  spe- 
cial protective  and  aggressive  devices,  etc.  In  insects  as  a 
whole,  the  environment  of  the  larva  or  nymph  and  that  of  the 
adult  are  very  different,  as  in  the  dragon  fly  or  the  butterfly, 
and  the  larvae  are  modified  in  a  thousand  ways  for  their  own 
immediate  advantage,  without  any  direct  reference  to  the 
needs  of  the  imago. 

The  chief  purpose,  so  to  speak,  of  the  larva  is  to  feed  and 
grow,  and  the  largest  modifications  of  the  larva  depend  upon 
nutrition.  Take  as  one  extreme,  the  legless,  headless,  fleshy 
and  sluggish  maggot,  embedded  in  an  abundance  of  food,  and 
as  the  other  extreme  the  active  and  "  wide-awake  "  larva  of 
a  carabid  beetle,  dependent  for  food  upon  its  own  powers  of 
sensation,  locomotion,  prehension,  etc.,  and  obliged  meanwhile 
to  protect  or  defend  itself.  Between  these  extremes  come 
such  forms  as  caterpillars,  active  to  a  moderate  degree.  The 
great  majority  of  larval  characters,  indeed,  are  correlated  with 
food  habits,  directly  or  indirectly;  directly  in  the  case  of  the 
mouth  parts,  sensory  and  locomotor  organs,  and  special  struc- 
tures for  obtaining  special  food ;  indirectly,  as  in  respiratory 
adaptations  and  protective  structures,  these  latter  Ijeing  numer- 
ous and  varied. 

Larvae  that  live  in  concealment,  as  those  that  burrow  in  the 
ground  or  in  plants,  have  few  if  any  special  protective  struc- 
tures ;  active  larvre.  as  those  of  Carabidse,  have  an  armor-like 
integument,  but  owe  their  protection  from  enemies  chiefly  to 
their  powers  of  locomotion  and  their  aversion  to  light  {nega- 
tive phototropisin)  ;  various  acjuatic  nymphs  (Zaitha,  Odonata  ) 
are  often  coated  with  mud  and  therefore  difiicult  to  distin- 
guish so  long  as  they  do  not  mo\'e;  caddis  worms  are  con- 
cealed in  their  cases,  and  caterpillars  are  often  sheltered  in  a 
leafy  nest.  There  is  no  reason  to  suppose  that  insects  conceal 
themselves  consciously,  however,  and  one  is  not  warranted  in 
speaking  of  an  instinct  for  concealment  in  the  case  of  insects — 
since  everything  goes  to  show  that  the  propensity  to  hide, 
though  advantageous   indeed,    is   simply   a   reflex,    inevitable. 


DEVELOPMENT  1 67 

negative  reaction  to  light  (iicgatk'c  f^Jioloiropisni)  or  a  positive 
reaction  to  contact  {/^ositrrc  iliigiiiofropisin) . 

Exposed,  sedentary  larv;e.  as  those  of  many  Lepidop- 
tera  and  Coleoptera,  often  exhil)it  highly  developed  protective 
adaptations.  Caterpillars  may  be  colored  to  match  their  sur- 
ronndings  and  may  resemble  twigs,  bird-dung,  etc. ;  or  larv?e 
may  possess  a  disagreeable  taste  or  repellent  fluids  or  spines, 
these  odious  qualities  being  frequently  associated  with  warn- 
ing colors. 

Larvae  need  protection  also  against  adverse  climatal  condi- 
tions, especially  low  temperature  and  excessive  moisture. 
The  thick  hairy  clothing  of  some  hibernating  caterpillars,  as 
Isia  (Pyrrliarcfia)  Isabella,  doubtless  serves  to  mollify  sudden 
changes  of  temperature.  Naked  cutworms  hibernate  in  well- 
sheltered  situations,  and  the  grubs  of  the  common  "  May 
beetles,"  or  "  June  bugs,"  burrow  down  into  the  ground  below 
the  reach  of  frost.  Ordinary  high  temperatures  have  little 
effect  upon  larwx,  except  to  accelerate  their  growth.  Exces- 
sive moisture  is  fatal  to  immature  insects  in  general — conspicu- 
ously fatal  to  the  chinch  bug.  Rocky  ^Mountain  locust,  aphids 
and  sawfly  larvae.  The  effect  of  moisture  may  be  an  indirect 
one,  however;  thus  moisture  may  favor  the  development  of 
bacteria  and  fungi,  or  a  heavy  rain  may  be  disastrous  not  only 
by  drowning  larvae,  but  also  by  washing  them  off  their  food 
plants. 

As  a  result  of  secondary  adaptive  modifications,  larvse 
may  differ  far  more  than  their  imagines.  Thus  Plafygastcr  in 
its  extraordinary  first  larval  form  (Fig.  218)  is  entirely  unlike 
the  larvae  of  other  parasitic  Hymenoptera,  reminding  one, 
indeed,  of  the  crustacean  Cyclops  rather  than  the  larva  of  an 
insect.     As  Lubbock  has  said,  the  characters  of  a  larva  depend 

( 1 )  upon  the  group  of  insects  to  which  the  larva  belongs  and 

(2)  upon  the  special  environment  of  the  larva. 

Pupa. — The  term  pupa  is  strictly  applicable  to  holometabo- 
lous  insects  only.  Most  Lepidoptera  and  many  Diptera  have 
an  obtect  pupa  (Fig.  212),  or  one  in  which  the  appendages 


i68 


ENTOMOLOGY 


Fig.  212. 


Obtect  pupa  of  milk- 
weed butterfly,  Anosia 
ple.vippus,   natural   size. 


and  body  are  compactly  united ;  as  distinguished  from  the  free 
pupa  of  Neuroptera,  Trichoptera,  Coleoptera  and  others,  in 
which  the  appendages  are  free  (Fig.  203).  This  distinction, 
however,  cannot  always  be  drawn  sharply.  Diptera  present 
also  the  coarctatc  type  of  pupa  (Fig. 
204),  in  which  the  pupa  remains  en- 
closed in  the  old  larval  skin,  or  pnpa- 
riiim. 

Pupal  characters,  though  doubtless  of 
great  adaptive  and  phylogenetic  signifi- 
cance, have  received  but  little  attention. 
Lepidopterous  pup?e  present  many  puz- 
zling characters,  for  example,  an  eye- 
like structure  (Fig.  213)  suggesting 
an  ancestral  active  condition,  such  as 
still  occurs  among  heterometabolous  in- 
sects. 
Pupation  of  a  Caterpillar, — The  process  of  pupation  in 
a  caterpillar  has  been  carefully  observed  by  Riley.  The  cater- 
pillar of  the  milkweed  butterfly  (PI.  i.  A)  spins  a  mass  of 
silk  in  which  it  entangles  its  suranal  plate  and  anal  prolegs 
and  then  hangs  downward,  bending  up 
the  anterior  part  of  the  body  (B),  which 
gradually  becomes  swollen.  The  skin 
of  the  caterpillar  splits  dorsally,  from 
the  head  backward,  and  is  worked  back 
toward  the  tail  (C  and  D)  by  the  con- 
tortions of  the  larva. 

The  way  in  which  the  pupa  becomes  at- 
tached to  its  silken  support  is  rather  com- 
plex. Briefly,  while  the  larval  skin  still 
retains  its  hold  on  the  support,  the  posterior  end  of  the  pupa 
is  withdrawn  from  the  old  integument  and  by  the  vigorous 
whirling  and  twisting  of  the  body  the  hooks  of  the  terminal 
cremaster  of  the  pupa  are  entangled  in  the  silken  support.  At 
first  the  pupa  is  elongate  (E)  and  soft,  but  in  an  hour  or  so 


Fig, 


Head  of  chrysalis  of 
Papilio  polyxcnes,  to 
show  eye-like  structure. 
Enlarged. 


PLATK  1. 


Successive   stages   in    the 


nation    of   the    milkweed   caterpillar,    Anosin   f^lcvippn 
Natural   size. 


DEVELOPMENT 


169 


it  has  contracted,  hardened,  and  assumed  its  characteristic  form 
and  coloration  (/•"). 

Pupal  Respiration. — Except  under  special  conditions,  pupre 
breathe  by  means  of  ordinary  abdominal  spiracles.     Aquatic 
pupai    have    special    res])iratory    org-ans. 
such  as  the  tracheal  filaments  of  Siiiiu- 
liuiii     (Fig".    -230),    and    the    respiratory 
tubes  of  Ciilrx  (Fig.  229). 

Pupal  Protection.  —  Inactive  and 
helpless,  most  puprc  are  concealed  in  one 
wav  or  another  from  the  observation  of 
enemies  and  are  protected  from  mois- 
ture, sudden  changes  of  temperature, 
mechanical  shock  and  other  adverse  in- 
fluences. The  larv?e  of  many  moths 
burrow  into  the  ground  and  make  an 
earthen  cell  in  which  to  pupate ;  a  large 
number  of  coleopterous  larv;e  (  Lac  Jin  o- 
stcrna,  Osmodcrma,  Passaliis,  Liicaiiiis, 
etc.)  make  a  chamber  in  earth  or  wood,  the  walls  of  the  cell 
being  strengthened  with  a  cementing  fluid  or  more  or  less 
silk,  forming  a  rude  cocoon.  Silken  cocoons  are  spun  by 
some  Xeuroptera  ( Chrysopidae,  Fig.  214),  by  Trichoptera 
(whose  cases  are  essentially  cocoons),  Lepidoptera,  a  few  Co- 
leoptera  (as  CuvcuWonidx,  Doiiacia) ,  some  Diptera  (as  Cecido- 
myiidse),  Siphonaptera,  and  many  Hymenoptera  (for  exam- 
ple, Tenthredinid?e,  Ichneumonid?e,  wasps,  bees  and  some 
ants). 

The  cocoon-making-  instinct  is  most  highly  developed  in 
Lepidoptera  and  the  most  elaborate  cocoons  are  those  of  Satur- 
niidse.  The  cocoon  of  Saniia  cecropia  is  a  tough,  w^ater-proof 
structure  and  is  double  (Fig.  215),  there  being  tw^o  air  spaces 
around  the  pupa ;  thus  the  pupa  is  protected  against  moisture 
and  sudden  changes  of  temperature  and  from  most  birds  as 
well,  though  the  downy  woodpecker  not  infrequently  punc- 
tures the  cocoon.     S.   cecropia   binds  its  cocoon  firmly  to  a 


Cocoon  of  Clirysopa, 
after  emergence  of 
i  m  a  g  o.  Slightly  en- 
larged. 


70 


ENTOMOLOGY 


twig;  Tvopcca  luna  and  Tcica  poIypJicnius  spin  among  leaves, 
and  their  cocoons  (with  some  exceptions)  fah  to  the  ground; 
Callosainia  proiucthca,  whose  cocoon  is  covered  with  a  curved 
leaf,  fastens  the  leaf  to  the  twig  with  a  wrapping  of  silk,  so 
that  the  leaf  with  its  burden  hangs  to  the  twig  throughout  the 
winter.  The  leaves  surrounding  cocoons  may  render  them 
inconspicuous  or  may  serve  merely  as  a  foundation  for  the 
cocoon.     While  silk  and  often  a  water-proof  gum  or  cement 

Fig.  215. 


Cocoon   of   Samia   cccropia,   cut   open   to    show    the    two    silken   layers 
pupa.      Natural   size. 


id   the    enclosed 


form  the  basis  of  a  cocoon,  much  foreign  material,  such  as  bits 
of  soil  or  wood,  is  often  mixed  in ;  the  cocoons  of  many  com- 
mon Arctiidae.  as  Diacrisia  z'irgiiiica  and  Isia  isabcUa.  consist 
principally  of  hairs,  stripped  from  the  body  of  the  larva. 

Butterflies  have  discarded  the  cocoon,  the  last  traces  of 
which  occur  in  Hesperiidse,  which  draw  together  a  few  leaves 
with  a  scanty  supply  of  silk  to  make  a  flimsy  substitute  for  a 
cocoon.  Papilionid  and  pierid  pupcT  are  supported  by  a  silken 
girdle  (Fig.  2y) .  and  nymphalid  chrysalides  hang  freely  sus- 
pended by  the  tail  (Fig.  212). 

Cocoon-Spinning. — The  caterpillar  of  Tclca  polyplicuius 
"  feels  with  its  head  in  all  directions,  to  disco\-er  any  leaves 
to  which  to  attach  the  fibres  that  are  to  give  form  to  the  co- 
coon.     If  it  finds  the  place  suitable,  it  begins  to  wind  a  layer 


DEVELOPMENT  I/I 

of  silk  around  a  Iwii;-,  then  a  fil^re  is  attached  to  a  leaf  near 
by,  and  1)y  many  times  doubling  this  fibre  and  making  it 
shorter  ever}-  time,  the  leaf  is  made  to  approach  the  twig  at 
the  distance  necessary  to  build  the  cocoon;  two  or  three  leaves 
are  disposed  like  this  one,  and  then  fibres  are  spread  between 
them  in  all  directions,  and  soon  the  ov(^id  form  of  the  cocoon 
distinctly  appears.  This  seems  to  be  the  most  difficult  feat 
for  the  worm  to  accomplish,  as  after  this  the  work  is  simply 
mechanical,  the  cocoon  being  made  of  regular  layers  of  silk 
united  by  a  gummy  substance.  The  silk  is  distrllnited  in  zig- 
zag lines  of  about  one-eighth  of  an  inch  long-.  When  the 
cocoon  is  made,  the  worm  will  ha\'e  mo\-ed  his  head  to  and 
fro,  in  order  to  distribute  the  silk,  about  two  hundred  and 
fifty-four  thousand  times.  After  about  half  a  day's  work,  the 
cocoon  is  so  far  completed  that  the  worm  can  hardly  be  dis- 
tinguished through  the  fine  texture  of  the  wall ;  then  a  gummy 
resinous  substance,  sometimes  of  a  light  brown  color,  is  spread 
over  all  the  inside  of  the  cocoon.     The  larva  continues  to  work 

for   four   or  five   days,   hardly  taking  a 

•^    '        ^      •;,  '^  Fig.  2i6. 

few  mmutes  ot  rest,  and  nnally  another 

coating    is    spun    in    the    interior,    when  Py-'I^ 

the  cocoon  is  all  finished  and  completely  Wl  p3k 

air  tight.     The  fibre  diminishes  in  thick-  ^:^£^ 

ness    as    the    completion    of    the    cocoon  liZss^^ 

advances,  so  that  the  last  internal  coat-  p~^7 

ing  is  not  half  so  thick  and   so   strong  p^^^^^ 

as  the  outside  ones."      (Trouvelot.)  ^|^^ 

Emergence    of    Pupa, — Subterranean  if 

pup?e   wriggle   their  way   to   the  surface      Subterranean     pupa    of 

-      ,  ,  .  ,       '  ,  .  ,        ^          .  Anisota.      Enlarged. 

ot  the  ground,  often  by  the  aid  of  spines 

(Fig.  216)  that  catch  successively  into  the  surrounding  soil. 
These  locomotor  spines  may  occur  on  almost  any  part  of  the 
pupa,  but  occur  commonly  on  the  abdominal  segments,  as  in 
lepidopterous  pupcC ;  the  extremity  of  the  abdomen,  also,  bears 
frequently  one  or  more  spinous  projections,  as  in  Tipulidae, 
Carabidse  and  Lepidoptera,  to  assist  the  escape  of  the  pupa. 


1/2  ENTOMOLOGY 

These  structures  are  found  also  in  pup?e,  as  those  of  Sesiidre, 
that  force  their  way  out  of  the  stems  of  plants  in  which  the 
larvK  ha^'e  lived.  The  emergence  from  the  cocoon  is  accom- 
plished in  some  cases  by  the  pupa,  in  others  by  the  imago. 
Hemerobiidse,  Trichoptera  and  the  primitive  lepidopteron 
Eriocephala  use  the  pupal  mandibles  to  cut  an  opening  in  the 
cocoon;  while  many  lepidopterous  pupae  have  on  the  head  a 
beak  for  piercing  the  cocoon,  or  teeth  for  rending  or  cutting 
the  silk. 

Eclosion. — During  the  last  few  hours  before  the  emer- 
gence of  a  butterfly  the  colors  of  the  imago  develop  and  may 
be  seen  through  the  transparent  skin  of  the  chrysalis  (PI. 
2,  A).  No  movement  occurs,  however,  until  several  seconds 
before  emergence;  then,  after  a  few  convulsive  movements  of 
the  legs  and  thorax  of  the  imprisoned  insect,  the  pupa  skin 
breaks  in  the  region  of  the  tongue  and  legs  (5),  a  secondary 
split  often  occurs  at  the  back  of  the  thorax,  and  the  butterfly 
emerges  {C-E)  with  moist  body,  elongated  abdomen  and 
miniature  wings.  Hanging  to  the  empty  pupa  case  (F),  or 
to  some  other  available  support,  the  insect  dries  and  its  wings 
gradually  expand  {G,  H)  through  the  pressure  of  the  blood. 
At  regular  intervals  the  abdomen  contracts  and  the  wings  fan 
the  air,  and  sooner  or  later  a  drop  or  two  of  a  dull  greenish 
fluid  (the  meconium)  is  emitted  from  the  alimentary  canal. 
The  expansion  of  the  wings  takes  place  rapidly,  and  in 
less  than  an  hour,  as  a  rule,  they  have  attained  their  full 
size  (/). 

T.  polyphcmiis  is  "  provided  with  two  glands  opening  into 
the  mouth,  which  secrete  during  the  last  few  days  of  the  pupa 
state,  a  fluid  which  is  a  dissolvent  for  the  gum  so  firmly  unit- 
ing the  fibres  of  the  cocoon.  This  liquid  is  composed  in  great 
part  of  bombycic  acid.  When  the  insect  has  accomplished  the 
work  of  transformation  which  is  going  on  under  the  pupa 
skin,  it  manifests  a  great  activity,  and  soon  the  chrysalis  cover- 
ing bursts  open  longitudinally  upon  the  thorax ;  the  head  and 
legs  are  soon  disengaged,  and  the  acid  fluid  flows  from  its 


PLATE  II. 


Successive   stages   in   the  emergence  of  the  milkweed  butterfly,   Anosia  l<lcxlppus,   from 
the  clirysalis.      Natural   size. 


DEVELOPMENT  1/3 

mouth,  wcttiiii^'  ibe  inside  of  the  cocoon.  The  ])r(^cess  of  ex- 
cUision  from  the  cocoon  lasts  for  as  much  as  half  an  hour. 
The  insect  seems  to  be  instinctively  aware  [  ?]  that  some  time 
is  required  to  dissolve  the  gum.  as  it  does  not  make  any  attempt 
to  open  the  fibres,  and  seems  to  wait  with  patience  this  event. 
\\nien  the  liquid  has  fully  penetrated  the  cocoon,  the  pupa  con- 
tracts its  l:)odv,  and  pressing"  the  hinder  end,  which  is  furnished 
with  little  hooks,  against  the  inside  of  the  cocoon,  f(jrcibly 
extends  its  body ;  at  the  same  time  the  head  pushes  hard  upon 
the  fibres  and  a  little  swelling  is  observed  on  the  outside. 
These  contractions  and  extensions  of  the  body  are  repeated 
many  times,  and  more  fluid  is  added  to  soften  the  gum,  until 
under  these  efforts  the  cocoon  swells,  and  finally  the  fibres 
separate,  and  out  comes  the  head  of  the  moth.  In  an  instant 
the  legs  are  thrust  out,  and  then  the  whole  body  appears ;  not 
a  fibre  has  been  ])roken,  they  have  only  been  separated. 

"  To  observe  these  phenomena,  I  had  cut  open  with  a  razor 
a  small  portion  of  a  cocoon  in  which  was  a  living  chrysalis 
nearly  ready  to  transform.  The  opening  made  was  covered 
with  a  piece  of  mica,  of  the  same  shape  as  the  aperture,  and 
fixed  to  the  cocoon  with  mastic  so  as  to  make  it  solid  and  air- 
tight ;  through  the  transparent  mica,  I  could  see  the  move- 
ments of  the  chrysalis  perfectly  well. 

"  When  the  insect  is  out  of  the  cocoon,  it  immediately  seeks 
for  a  suitable  place  to  attach  its  claws,  so  that  the  wings  may 
hang  down,  and  by  their  own  weight  aid  the  action  of  the 
fluids  in  developing  and  unfolding  the  very  short  and  small 
pad-like  wings.  Every  part  of  the  insect  on  leaving  the  co- 
coon, is  perfect  and  with  the  form  and  size  of  maturity,  except 
the  pad-like  wings  and  swollen  and  elongated  abdomen,  which 
still  gives  the  insect  a  worm-like  appearance ;  the  abdomen  con- 
tains the  fluids  which  flow  to  the  wings. 

"  \\dien  the  still  immature  moth  has  found  a  suitable  place, 
it  remains  quiet  for  a  few  minutes,  and  then  the  wings  are  seen 
to  grow  very  rapidly  by  the  afflux  of  the  fluids  from  the  abdo- 
men.    In  about  twentv  minutes   the  wings  attain   their   full 


174  ENTOMOLOGY 

size,  but  they  are  still  like  a  piece  of  wet  cloth,  without  con- 
sistency and  firmness,  and  as  yet  entirely  unfit  for  flight,  but 
after  one  or  two  hours  they  become  sufficiently  stiff,  assuming 
the  beautiful  form  characteristic  of  the  species."  (Trouvelot.) 
The  expansion  of  the  wing  is  due  to  blood-pressure  brought 
about  chiefly  by  the  abdominal  muscles.  In  the  freshly- 
emerged  insect,  the  two  membranes  of  the  wing  are  corru- 
gated, and  expansion  consists  in  the  flattening  out  of  these 
folds.  The  wing  is  a  sac,  which  would  tend  to  enlarge  into 
a  balloon-shaped  bag,  were  it  not  for  hypodermal  fibers  which 
hold  the  wing-membranes  closely  together  (Mayer).  Samia 
cccropia  also  uses  a  dissolvent  fluid;  Tropcca  hum,  PJiilosaniia 
cyiithia  and  others  cut  and  force  an  opening  through  the  cocoon 
by  means  of  a  pair  of  saw-like  organs,  one  at  the  base  of  each 
front  wing. 

Hypermetamorphosis. — In  a  few  remarkable  instances, 
metamorphosis  involves  more  than  three  stages,  owing  to  the 
existence  of  supernumerary  larval  forms.  This  phenomenon 
of  hypcniictamorpliosis  occurs  notably  in  the  coleopterous 
genera  Mcloc,  Epicauta,  Sitaris,  RhipipJiorus  and  Sfylops,  in 
male  Coccid?e  and  several  parasitic  Hymenoptera. 

In  Mcloc,  as  described  by  Riley,  the  newly-hatched  larva 
(triunguliii  form)  is  active  and  campodea-form.  It  climbs 
upon  a  flower  and  thence  upon  the  body  of  a  bee  (AiifJio- 
phora),  which  carries  it  to  the  nest,  where  it  eats  the  egg  of 
the  bee.  After  a  moult,  the  larva  though  still  six-legged,  has 
become  cylindrical,  fleshy  and  less  active,  resembling  a  lamelli- 
corn  larva;  it  now  appropriates  the  honey  of  the  bee.  With 
plenty  of  rich  food  at  hand  the  larva  becomes  sluggish,  and 
after  another  moult  appears  as  a  pseudo-pupa,  with  function- 
less  mouth  parts  and  atrophied  legs.  From  this  pseudo-pupa 
emerges  a  third  larval  form,  of  the  pure  cruciform  type,  fat 
and  apodous  like  the  bee-larvre  themselves.  After  these  four 
distinct  stages  the  larva  becomes  a  pupa  and  then  a  beetle. 

Epicauta,  another  meloid,  has  a  similar  history.  The  tri- 
uiigitlin  (Fig.  217,  A)  of  E.  z'ittafa  burrows  into  an  egg'-pod 


DEVELOPMENT 


'75 


of  Mclaiu)plus  diffcrcutiaUs  and  eats  the  eL;i;s  of  that  g'rass- 
hopper.  After  a  niDult  the  second  larz'd  (carabidoid  form) 
appears;  this  {B)  is  soft,  with  re(hice(l  lei^'s  aii<l  niontli  parts 
and  less  acti\-e  than  the  trinni^nhn.  A  second  monit  and  the 
scarabaddiud   form  of  the  second  h\r\a   is  assnmed ;  the  lees 


Fig. 


Stages  in  the  hypermetamorphosis  of  Epicanta.  A,  ti-iungulin;  B,  carabidoid  stage 
of  second  larva;  C,  ultimate  stage  of  second  larva;  D,  coarctate  larva;  E,  pupa;  F, 
imago.  E  is  species  cinerea;  the  others  are  z'itfata.  All  enlarged  except  F. — After 
Riley,   from  Trans.   St.   Louis  Acad.   Science. 


and  mouth  parts  are  now  rudimentary  and  the  body  more 
compact  than  before.  A  third  and  a  fourth  moult  occur  with 
little  change  in  the  form  of  the  second  larva,  which  is  now^  in 
its  nltiniatc  stage  (C).  After  the  fifth  moult,  however,  the 
coarctate  larva,  or  pseudo-pupa,  appears;  this  (D)  hibernates 
and  in  spring  sheds  its  skin  and  becomes  the  tJiird  larva,  which 
soon  transforms  to  a  true  pupa  (£),  from  which  the  beetle 
{F)  shortly  emerges.  Thus  the  pupal  stage  is  preceded  by 
at  least  three  distinct  larval  stages. 

In  the  anomalous  l;)eetle  Stxlops,  the  males  are  winged,  but 
the  females  are  maggot-like  and  sedentary,  living  in  the  bodies 
of  bees  and  wasps.      Packard  found  as  many  as  three  hundred 


176 


ENTOMOLOGY 


triimgiilin  larva;  issuing  from  a  female  Sfylops  in  the  body  of 
an  Aiidrcua.  The  further  life  history  of  Stylo ps  is  but  im- 
perfectly known ;  probajbly  the  triungulin  climbs  upon  a  bee 
or  a  wasp  and  enters  its  body,  after  the  manner  of  the  Euro- 
pean Rliipiphonis  paradoxus,  whose  life-history  is  much  bet- 
ter understood. 

The  most  extraordinary  metamorphoses  have  been  found 
among  parasitic  Hymenoptera.  as  in  Platygastcr,  a  proctotry- 
pid  which  infests  the  larva  of  Cccidoiiiyia.  The  egg  of  Platy- 
pasfcr,  according  to  Ganin,  hatches  into  a  larva  of  bizarre 


Fig.  2 1 8. 


Stages  in  the  hypermetamorphosis  of  Platygastcr.  A,  first  larva;  B,  second  larva; 
C,  third  larva;  a,  antenna;  b,  brain;  f,  fat-tissue;  /;,  hind  intestine:  )n,  mandible;  mo, 
mouth;  ins,  muscle;  n,  nerve  cord;  r,  reproductive  organ  of  one  side;  s,  salivary 
gland;   t,  trachea. — After  Ganin. 


form  (Fig.  218,  A),  suggesting  the  crustacean  Cyclops,  rather 
than  an  insect.  This  first  larva  has  a  blind  food  canal  and  no 
nervous,  circulatory  or  respiratory  systems.  After  a  moult 
the  outline  is  oval  [B),  and  there  are  no  appendages  as  yet, 
though  the  nervous  system  is  partially  developed.  Another 
moult,  and  the  third  larva  appears  (C),  elliptical  in  contour, 
■externally  segmented,  with  trachea^  and  a  pair  of  mandibles. 


DEVELOPMENT  1/7 

From  now  on,  the  development  is  essentially  like  that  of  other 
parasitic  Hymenoptera. 

E(|nally  anomalous  are  the  changes  undergone  by  ^0/3-- 
iiciiui.  a  proctotrypid  parasite  in  the  eggs  of  dragon  flies,  and 
by  the  proctotrypid  Tclcas,  which  affects  the  eggs  of  the  tree 
cricket  (Qicanfhiis).  In  all  these  cases  the  larvae  go  through 
changes  which  in  most  other  insects  are  confined  to  the  egg 
stage.  In  other  words,  the  lar\a  hatches  before  its  embryonic 
development  is  completed,  so  to  speak. 

Significance  of  Metamorphosis, — "  The  essential  features 
of  metamorphosis,"  says  Sharp,  "  appear  to  be  the  separation 
in  time  of  growth  and  development,  and  the  limitation  of  the 
reproductive  processes  to  a  short  period  at  the  end  of  the  indi- 
vidual life." 

The  simplest  insects,  Thysanura,  have  no  metamorphosis, 
and  show  no  traces  of  ever  having  had  one.  Hence  it  is  in- 
ferred that  the  first  insects  had  none ;  in  other  words,  the  phe- 
nomenon of  metamorphosis  originated  later  than  insects  them- 
selves. Successive  stages  in  the  evolution  of  metamorphosis 
are  illustrated  in  the  various  orders  of  insects. 

The  distinctive  mark  of  the  simplest  metamorphosis,  as  in 
Orthoptera  and  Hemiptera,  is  the  acquisition  of  w'ings ;  growth 
and  sexual  development  proceeding  essentially  as  in  the  non- 
metamorphic  insects  (Thysanura  and  Collembola).  Here  the 
development  of  wnngs  does  not  interfere  wnth  the  activity  of 
the  insect;  its  food  habits  remain  unaltered;  throughout  life 
the  environment  of  the  individual  is  practically  the  same. 
Even  when  considerable  difference  exists  between  the  nym- 
phal  and  imaginal  euA'ironments,  as  in  Ephemerida  and 
Odonata,  the  activity  of  the  individual  may  still  be  continu- 
ous, even  if  somewdiat  lessened  as  the  period  of  transforma- 
tion approaches. 

With  Neuroptera,  the  pupal  stage  appears.  In  these  and 
all  other  holometabolous  insects  the  larva  accumulates  a  sur- 
plus of  nutriment  sufficient  for  the  further  development,  which 
becomes  condensed  into  a  single  pupal  stage,  during  wdiich 
external  activity  ceases  temporarily. 
13 


178  ENTOMOLOGY 

With  the  increasing  contrast  between  the  organization  of 
the  larva  and  that  of  the  imago,  the  pupal  stage  gradually 
becomes  a  necessity.  Metamorphosis  now  means  more  than 
the  mere  acquisition  of  wings,  for  the  larva  and  the  imago 
have  become  adapted  to  widely  different  environments,  chiefly 
as  regards  food.  The  caterpillar  has  biting  mouth  parts  for 
eating  leaves,  while  the  adult  has  sucking  organs  for  obtaining 
liquid  nourishment :  the  maggot,  surrounded  by  food  that  may 
be  obtained  almost  without  exertion,  has  but  minimum  sensory 
and  locomotor  powers  and  for  mouth  parts  only  a  pair  of 
simple  jaws ;  as  contrasted  with  the  fly,  which  has  wings, 
highly  developed  mouth  parts  and  sense  organs,  and  many 
other  adaptations  for  an  environment  which  is  strikingly  un- 
like that  of  the  larva ;  so  also  in  the  case  of  the  higher  Hymen- 
optera,  where  maternal  or  family  care  is  responsible  for  the 
helpless  condition  of  the  larva. 

Thus  it  is  evident  that  the  change  from  larval  to  imaginal 
adaptations  is  no  longer  congruous  with  continuous  external 
activity;  a  quiescent  period  of  reconstruction  becomes  in- 
evitable. 

As  was  said,  the  cruciform  type  of  larva  has  been  derived 
from  the  thysanuriform  type,  the  strongest  evidence  of  this 
being  the  fact  that  among  hypermetamorphic  insects,  the 
change  from  the  one  to  the  other  takes  place  during  the  life- 
time of  the  individual.  Furthermore,  the  cruciform  condi- 
tion is  plainly  an  adaptive  one,  brought  about  by  an  abundant 
and  easily  obtainable  supply  of  food.  The  lack  of  a  thysa- 
nuriform stage  in  the  development  of  the  most  specialized 
cruciform  larvse,  as  those  of  flies  and  bees,  is  regarded  by 
Hyatt  and  Arms  as  an  illustration  of  the  general  principle 
known  as  "  acceleration  of  development,"  according  to  which 
newer  and  useful  adaptive  characters  tend  to  appear  earlier 
and  earlier  in  the  development,  gradually  crowding-  upon  and 
forcing  out  older  and  useless  characters.  In  connection  with 
this  subject,  the  appearance  of  temporary  abdominal  legs  in 
embryo  bees  is  significant,  as  indicating  an  ancestral  active 


DEVELOPMENT 


179 


Fig. 


condition.      In  accounting-  for  the  evolution  of  metamorpho- 
sis,   the    theory    of    natural    selection 
finds  one  of  its  most  important  appli- 
cations. 


3.  Internal  METAMORrnosEs 

In  Heterometahola.  the  internal 
post-embryonic  changes  are  as  di- 
rect as  the  external  changes  of 
form;  in  Holometahola,  on  the  con- 
trar)-.  not  all  the  larval  organs 
pass  directly  into  imaginal  organs, 
for  certain  larval  tissues  are  de- 
molished and  their  sul)stance  recon- 
structed into  imaginal  tissues.      Wdien 


Diagrammatic  transverse 

section  of  Corethra  larva,  to 
show  imaginal  buds  of  wings 
iw)  and  legs  (/) ;  h,  hypoder- 
mis;  i,  integument. — Modified 
from  Lang's  Lehrbttch. 


¥k 


Diagrammatic  transverse  sections  of  muscid  larvre,  to  show  imaginal  buds,  h,  lar- 
val hypodermis;  /,  larval  integument;  ih.  imaginal  hypodermis;  /,  imaginal  bud  of 
leg;   w,   imaginal   bud   of  wing.— Modified   from   Lang's  Lchrbuch. 


:8o 


ENTOMOLOGY 


indirect,  however,  the  internal  metamorphosis  is  nevertheless 
continuous  and  gradual,  without  the  abruptness  that  charac- 
terizes the  external  transformation.  In  the  lan'al  stage  ima- 
ginal  organs  arise  and  grow ;  in  the  pupal  stage  the  purely 
larval  organs  gradually  disappear  ^^•hile  the  imaginal  organs 
are  continuing  their  development. 

Phagocytes. — The    destruc- 

FlG.    221.  .  f        •' 

tion  of  larval  tissues,  or  his- 
tolysis, is  due  often  to  the 
amoeboid  blood  corpuscles, 
known  as  leucocytes  or  phago- 
cytes, which  attack  some  tis- 
sues and  absorb  their  mate- 
rial, but  later  are  themselves 
food  for  the  developing  imagi- 
nal tissues.  The  construction 
of  tissues  is  termed  histo- 
genesis. 

In  Coleoptera.  however,  the 
degeneration  of  the  larval  mus- 
cles is  entirely  chemical,  there 
being  no  evidence  of  phago- 
cytosis, according  to  Dr.  R.  S. 
Breed.  Berlese,  indeed,  goes 
so  far  as  to  deny  in  general 
the  destructive  action  of  leuco- 
cytes on  larval  tissues. 

Imaginal  Buds. — The  wings 
and  legs  of  a  fly  originate  in 
the  larva  in  the  form  of  cellu- 
lar masses,  or  iiiiagiiial  buds, 
as  \\"eismann  discovered.  Thus 
in  the  larva  of  Corethra,  there 
are  in  each  thoracic  segment  a  pair  of  dorsal  buds  and  a  pair 
of  ventral  buds  (Fig.  219),  each  bud  being  clearly  an  evagi- 
nation  of  the  hypodermis  at  the  bottom  of  a  previous  invagi- 


Imaginal  buds  of  full  grown  larva 
of  Pieris,  dorsal  aspect,  b,  brain ; 
m,  mid  intestine;  s^,  prothoracic 
spiracle;  s*,  first  abdominal  spiracle; 
sg,  silk  gland;  I,  prothoracic  bud; 
//,  bud  of  fore  wing;  ///,  bud  of 
hind  wing. — After  Gonin. 


DEVELOPMENT 


I8l 


nation.  Tlie  six  ventral  Inuls  form  the  legs  eventually;  of 
the  dorsal  l)U(ls.  the  middle  and  posterior  pairs  form,  resi)cc- 
tively,  the  wings  and  the  halteres,  and  the  anterior  pair  form 
the  pupal  respiratory  processes.  Each  imaginal  hud  is  situ- 
ated in  a  pcripodal  arrily.  the  wall  of  which  { pcripodal  mem- 
brane) is  continuous  with  the  general  hypoderniis;  as  the  legs 
and  wings  develop,  they  emerge  from  their  pcripodal  sacs  and 
hecome  free. 

In  Corcthra  hut  little  histolysis  occurs,  most  of  the  larval 
structures  passing'  directly  into  the  corresponding  structures 
of  the  adult.  Corcthra,  indeed,  is  in  many  respects  interme- 
diate between  heterometabolous  and  holometabolous  insects  as 
regards  its  internal  changes. 

Fig.  222. 


Section  through  left  hind  wing  in  larva  of  Picris  rapff,  the  section  being  a  frontal 
one  of  the  caterpillar;  tlie  base  of  the  wing  is  anterior  in  position,  and  the  apex 
posterior,     c,   cuticula;    /;,    hypodermis;   t,  trachea;   w,  developing  wing. — After   M.wer. 

Muscidae. — In  ]\Iuscid?e,  as  compared  with  Corcthra,  the 
imaginal  buds  are  more  deeply  situated,  the  peripodal  mem- 
brane forming  a  stalk  (Fig.  220),  and  the  processes  of  his- 
tolysis and  histogenesis  become  extremely  complicated.  The 
hypodermis,  muscles,  alimentary  canal  and  fat-body  are  grad- 
ually broken  down  and  remodeled,  and  part  of  the  respiratory 
system  is  reorganized,  thougii  the  dorsal  vessel  and  the  central 
nervous  system,  uninterrupted  in  their  functions,  undergo 
comparatively  little  alteration. 

The  imaginal  hypodermis  of  the  thorax  arises  from  thick- 


l82 


ENTOMOLOGY 


enings  of  the  peripodal  membrane  which  spread  over  the  lar- 
val   hypodermis,    while    the 
"^'  latter     is     gradually     being 

broken  down  by  the  leuco- 
cytes ;  in  the  head  and  abdo- 
men the  process  is  essen- 
tially the  same  as  in  the 
thorax,  the  new  hypodermis 
arising  from  imaginal  buds. 
Most  of  the  larval  mus- 
cles, excepting"  the  three 
pairs  of  respiratory  muscles, 
undergo  dissolution.  The 
imaginal  muscles  have  been 
traced  back  to  mesodermal 
cells  such  as  are  always  as- 
sociated with  imaginal  buds. 
Hymenoptera  and  Lepi- 
doptera. — The  internal 
transformation  in  Hymen- 
optera, according  to  Bugn- 
ion,  is  less  profound  than 
in  MuscidcT  and  more  ex- 
tensive than  in  Coleoptera 
and  Lepidoptera.  The  in- 
ternal metamorphosis  in 
Lepidoptera  resembles  in 
many  respects  that  of  Corc- 
tlira.  In  both  these  orders 
the  dorsal  pair  of  protho- 
racic  buds  is  absent.  In  a 
full-grown  caterpillar  the 
fundaments  of  the  imaginal 
legs  and  wings  (Fig.  221) 
may  be  seen,  the  wings  in  a 

frontal  section  of  the  larva  appearing  as  in  Fig.  222.     Many 


Internal  transformations  of  Sphinx  ligus- 
tri.  A,  larva;  B,  pupa;  C,  moth;  a,  aorta; 
an,  antenna;  b,  brain;  f,  fore  intestine; 
fr,  food  reservoir;  h,  hind  intestine;  ht, 
heart;  m,  mid  intestine;  mt,  Malpighian 
tubes;  p,  proboscis;  s,  suboesophageal  gang- 
lion; t,  testis;  tg,  thoracic  ganglia;  v,  ven- 
tral nerve  cord. — After   Newport. 


DEVELOPMENT  1 83 

of  the  details  of  the  internal  metamorphosis  in  Lepidoptera 
ha\e  heen  described  by  Ne\vi)ort  and  Gonin.  Figaire  223, 
after  Xewport,  shows  some  of  the  more  evident  internal  dif- 
ferences in  the  larva,  ])npa  and  imago  of  a  lepidopterous  insect. 
Significance  of  Pupal  Stage. — To  repeat — among-  holo- 
metabolons  insects  the  function  of  nutrition  becomes  relegated 
to  the  larval  stage  and  that  of  reproduction  to  the  imaginal 
stage.  Larva  and  imago  become  adapted  to  widely  different 
environments.  So  dissimilar  are  the  two  environments  that 
a  gradual  change  from  the  one  to  the  other  is  no  longer  pos- 
si])le;  the  revolutionary  changes  in  structure  necessitate  a  tem- 
porary cessation  of  external  activity. 


CHAPTER    IV 

ADAPTATIONS    OF   AQUATIC    INSECTS 

Ease,  versatility  and  perfection  of  adaptation  are  beauti- 
fully exemplified  in  aquatic  insects. 

Systematic  Position. — Aquatic  insects  do  not  form  a  sepa- 
rate group  in  the  system  of  classification,  but  are  distributed 
among  many  orders,  of  which  Plecoptera,  Ephemerida,  Odo- 
nata  and  Trichoptera  are  pre-eminently  aquatic.  One  third  of 
the  families  of  Heteroptera  and  less  than  one  fourth  those  of 
Diptera  are  more  or  less  acjuatic.  One  tenth  of  the  families 
of  Coleoptera  frequent  the^water  at  one  stage  or  another,  but 
only  half  a  dozen  genera  of  Lepidoptera.  A  few  Collembola 
live  upon  the  surface  of  water,  and  several  Hymenoptera, 
though  not  strictly  aquatic,  are  known  to  parasitize  the  eggs 
and  larvcT  of  aquatic  insects. 

The  change  from  the  terrestrial  to  the  aquatic  habit  has  been 
a  gradual  change  of  adaptation,  not  an  abrupt  one.  Thus  at 
present  there  are  some  tipulid  larvse  that  inhabit  comparatively 
dry  soil ;  others  live  in  earth  that  is  moist ;  many  require  a 
saturated  soil  near  a  body  of  water  and  many,  at  length,  are 
strictly  aquatic.  Among  beetles,  also,  similar  transitional 
stages  are  to  be  found. 

Food. — Insects  have  become  adapted  to  utilize  with  re- 
markable success  the  immense  and  varied  supply  of  food  that 
the  water  afifords.  Hosts  of  them  attack  such  parts  of  plants 
as  project  above  the  surface  of  the  water,  and  the  caterpillar 
of  Paraponyx  (Fig.  171)  feeds  on  submerged  leaves,  espe- 
cially of  Vallisncria,  being  in  this  respect  unique  among  Lepi- 
doptera. Hydrophilid  beetles  and  many  other  aquatic  insects 
devour  submerged  vegetation.  The  larvae  of  the  chrysomelid 
genus  Donacia  find  both  nourishment  and  air  in  the  roots  of 
aquatic  plants.     Various  Collembola  subsist  on  floating  algae, 

184 


ADAPTATIONS    OF    AQUATIC    INSECTS 


185 


and  Iarv;e  of  mosquitoes  and  l)lack-flies  on  microscopic  org-an- 
isms  near  the  surface,  while  larvae  of  CJiironoinus  find  food  in 
the  sediment  that  accumulates  at  the  bottom  of  a  body  of 
water. 

Predaceous  species  abound  in  the  water.     Nofoiiccta  (Fig. 
224)  approaches  its  i)rey  from  beneath,  clasps  it  with  the  front 


Fig.  224. 


Fig.  225. 


Backsvvimmer,    Notonccta   insulata, 
natural   size. 


Water-skater,  Ccrris  re, 


natural  size. 


pair  of  legs  and  pierces  it.  Ncpa  and  Ranatva  likewise  have 
prehensile  front  legs  along  with  powerful  piercing  organs. 
Bclostoina  and  Bcnacus  (Fig.  22)  even 
kill  small  fishes  by  their  poisonous  punc- 
tures. Some  other  kinds,  as  the  water- 
skaters  (GerridcC,  Fig.  225),  depend  on 
dead  or  disabled  insects.  The  species  of 
Hydrophihis  (Fig.  226)  are  to  some  ex- 
tent carnivorous  as  larvae  but  phytopha- 
gous as  imagines-,  while  Dytiscidse  are  car- 
nivorous throughout  life.  Aquatic  insects 
eat  not  only  other  insects,  but  also  worms, 
crustaceans,  mollusks  or  any  other  avail- 
able animal  matter. 

Even  aquatic  insects  are  not  exempt 
from  the  attacks  of  parasitic  species.  A 
few     Hymenoptera     actually     enter     the 

water  to  find  their  victims,  for  example,  the  ichneumon  Agrio- 
typiis,  which  lays  its  eggs  on  the  larvae  of  caddis  flies. 


Hydro[>hilus    triangularis, 
natural   size. 


i86 


ENTOMOLOGY 


Locomotion. — Excellent  adaptations  for  aquatic  locomo- 
tion are  found  in  the  common  Hydro pJiihis  triangularis  (Fig. 
226).  Its  general  form  reminds  one  of  a  boat,  and  its  long 
legs  resemble  oars.  The  smoothly  elliptical  contour  and  the 
polished  surface  serve  to  lessen  friction.  Owing  to  the  form 
of  the  body  (Fig.  22"/,  A)  and  the  presence  of  a  dorsal  air- 


FlG 


Transverse    sections   of    {A) 


A  B 

Hydropliilus  and    (S)    Notonccta. 
tron;    /.    metathoracic   leg. 


elytron;    h,   hemely- 


chamber  under  the  elytra,  the  back  of  the  insect  tends  to  re- 
main uppermost,  while  in  Notonccta  (Fig.  227,  B)  ,on  the  other 
hand,  the  conditions  are  reversed,  and  the  insect  swims  with 
its  back  downward.  The  legs  of  HydropJiilns,  excepting  the 
first  pair,  are  broad  and  thin  (Fig.  228,  A)  and  the  tarsi  are 
fringed  with  long  hairs.  When  swimming,  the  "  stroke  "  is 
made  by  the  flat  surface,  aided  by  the  spreading  hairs ;  but  on 
the  "  recover,"  the  leg  is  turned  so  as  to  cut  the  water,  while 
the  hairs  fall  back  against  the  tarsus  from  the  resistance  of  the 
water,  as  the  leg  is  being  drawn  forward.  The  hind  legs, 
being  nearest  the  center  of  gravity,  are  of  most  use  in  swim- 
ming, though  the  second  pair  also  are  used  for  this  purpose ; 
indeed,  a  terrestrial  insect,  finding  itself  in  the  water,  instinc- 
tively relies  upon  the  third  pair  of  legs  for  locomotion.  Hy- 
drophilus  uses  its  oar-like  legs  alternately,  in  much  the  same 
sequence  as  land  insects,  but  Cybistcr  and  other  Dytiscidae, 
which  are  even  better  adapted  than  Hydro philus  for  acjuatic 
locomotion,  move  the  hind  legs  simultaneously,  and  therefore 
can  swim  in  a  straight  line,  without  the  wobbling  and  less 
economical  movements  that  characterize  HydropJiilns. 


ADAPTATIONS    OF    AQUATIC    INSECTS 


187 


Larvne  of  niosciniloes  pr()[)el  themseh-es  by  means  of  lash- 
ing, or  undulatory,  movements  of  the  abdomen.  A  peculiar 
mode  of  locomotion  is  found  in  dragon  lly  nymphs,  which 
project  themselves  by  forcibly  ejecting  a  stream  of  water  from 
the  anus. 

On  account  of  the  large  amount  of  air  that  they  carry  about, 
most  aquatic  imagines  are  lighter  than  the  water  in  which  they 

Fk;.  228. 


Left   hind   legs   of   aquatic   beetles.     A,    hh 
hit  us;   c,    coxa;    /,    femur;    s,    spur; 


droplnlus 
t,    tarsus 


Mignlar 
.   tibia: 


B,    Cybisfci 
trochanter 


live,  and  therefore  can  rise  without  effort,  but  can  descend  only 
by  exertion,  and  can  remain  below  only  by  clinging  to  chance 
stationary  objects.  The  mosquito  larva  (Fig.  229,  ^)  is  often 
heavier  than  water,  but  the  pupa  (Fig.  229,  B)  is  lighter,  and 
remains  clinging  to  the  surface  film. 

The  tension  of  this  surface  film  is  sufticient  to  support  the 
weight  of  an  insect  up  to  a  certain  limit,  provided  the  insect 


i88 


ENTOMOLOGY 


Fig.  229. 


has  some  means  of  keeping  its  body  dry.  This  is  accom- 
phshed  usually  by  hairs,  set  together  so  thickly  that  water 
cannot  penetrate  between  them. 
As  the  legs  and  body  of  Gcrris 
are  rendered  water-proof  by  a  vel- 
vety clothing  of  hairs,  the  insect, 
though  heavier  than  water,  is  able 
to  skate  about  on  the  surface. 
Gyrimis,  by  means  of  a  similar 
adaptation,  can  circle  about  on  the 
surface  film,  and  minute  collem- 
bolans  leap  aljout  on  the  surface  as 
readily  as  on  land. 

The  modifications  of  the  legs 
for  swimming  have  often  impaired 
their  usefulness  for  walking,  so 
that  many  aquatic  Coleoptera  and 
Hemiptera  can  move  but  awk- 
wardly on  land,  \\dien  walking, 
it  is  interesting  to  note,  Cybisfcr 
and  some  other  aquatic  forms  no 
longer  move  their  hind  legs  simul- 
taneously as  they  do  in  swimming, 
but  use  them  alternately,  like  ter- 
restrial species. 

The  adaptations  for  swimming 
do  not  necessarily  affect  the  power 
of  flight.  Dytiscus,  Hydrophilus, 
Gyriuiis,  Notonccta,  Bcnaciis  and 
many  other  Coleoptera  and  Hemip- 
Larva   ^A)   and  pupa   (B)   of     ^cra  Icavc  the  water  at  night  and 

mosquito,    Culex  pipicns.     r,   respi-        fly  arOUUd,  oftCU  bciug  fouud  about 
ratory   tube;    t,    tracheal   gills. 


Respiration. — Aquatic  insects  have  not  only  retained  the 
primitive,  or  open  (Jwlopiicitsfic) ,  type  of  respiration,  charac- 


ADAPTATIONS    OF    AQUATIC    INSECTS  1 89 

terized  by  the  presence  of  spiracles,  but  have  also  developed 
an  adaptive,  or  closed  {apiicustic) ,  type,  for  ntilizini;-  air  that 
is  mixed  with  water. 

Through  minor  modifications  of  structure  and  habit,  many 
holopneustic  insects  have  become  fitted  for  an  aquatic  life.  In 
these  instances  the  insects  have  some  means  of  carrying  down 
a  supply  of  air  fn^n  the  surface  of  the  water.  Thus  Noto- 
nccta  bears  on  its  bcxly  a  silvery  film  of  air  entangled  in  closely 
set  hairs,  which  exclude  the  water.  Gyriiius  descends  with  a 
bublile  of  air  at  the  end  of  the  abdomen.  Dyfiscus  and  Hy- 
drophUiis  have  each  a  capacious  air-space  between  the  elytra  and 
the  abdomen,  into  which  space  the  spiracles  open.  Ncpa  and 
Ranatra  have  each  a  long  respiratory  organ  composed  of  two 
vah-es.  which  lock  together  to  form  a  tube  that  communicates 
with  the  single  pair  of  spiracles  situated  near  the  end  of  the 
abdomen.  The  mosquito  larva,  hanging  from  the  surface 
film,  breathes  through  a  cylindrical  tube  (Fig.  229,  A,  r)  pro- 
jecting from  the  penultimate  abdominal  segment ;  the  pupa, 
however,  bears  a  pair  of  respiratory  tubes  on  the  back  of  the 
thorax  (Fig.  229,  5.  r,  r),  which  is  now^  upward,  probably  in 
order  to  facilitate  the  escape  of  the  fly.  The  rat-tailed  maggot 
(Eristalis) ,  three  quarters  of  an  inch  long,  has  an  extensile 
caudal  tube  seven  times  that  length,  containing  two  tracheae 
terminating  in  spiracles,  through  which  air  is  brought  down 
from  above  the  mud  in  wdiich  the  larva  lives.  Similarly,  in 
the  dipterous  larva,  Bitiacomorpha  clavipcs  (Fig.  172),  the 
posterior  segments  of  the  abdomen  are  attenuated  to  form  a 
long  respiratory  tube.  The  larva  of  Donacia  appears  to  have 
no  special  adaptations  for  aquatic  respiration  except  a  pair  of 
spines  near  the  end  of  the  body,  for  piercing  air  chambers  in 
the  roots  of  the  acjuatic  plants  in  which  it  dwells. 

The  simplest  kind  of  apneustic  respiration  occurs  in  aquatic 
nymphs  such  as  those  of  Ephemerida  and  Agrionidce,  whose 
skin  at  first  is  thin  enough  to  allow  a  difect  aeration  of  the 
blood.  This  cutaneous  respiration  is  possible  during  the  early 
life  of  many  aquatic  species. 


190 


ENTOMOLOGY 


Bronchial  respiration,  however,  is  the  prevalent  type  amon^ 
aquatic  nymphs  and  is  perhaps  the  most  important  of  their 
adaptive  characteristics.  Thin-walled  and  extensive  out- 
growths of  the  integument,  containing  tracheal  branches  or, 
rarely,  only  blood,  enable  these  forms  to  oljtahi  air  from  the 
water.  May  fly  nymphs  (Figs.  19,  A  ;  169),  with  their  ample 
waving  gills,  offer  familiar  examples  of  branchial  respiration. 
Tracheal  gills  are  \ery  diverse  in  form  and  situation,  occurring 
in  a  few  species  of  May  fly  nymphs  on  the 
thorax  or  head,  though  commonly  re- 
stricted to  the  sides  of  the  abdomen, 
where  they  occur  in  pairs  or  in  paired 
clusters  (Fig.  19,  A).  Caudal  gills  are 
found  in  agrionid  nymphs  (Fig.  170). 
The  aquatic  caterpillars  of  Paraponyx 
(Fig.  171)  are  unique  among  Lepidop- 
tera  in  having  gills,  which  are  filamentous 
in  this  instance. 

Caddis  worms,  enclosed  in  their  cases, 
maintain  a  current  of  water  by  means 
of  undulatory  movements  of  the  body, 
and  the  larvse  and  pupse  of  most  black  flies 
(Simuliid?e,  Fig.  230)  secure  a  continuous 
supply  of  fresh  air  simply  by  fastening 
themselves  to  rocks  in  swiftly  flowing  streams. 

Rectal  respiration  is  highly  developed  in  odonate  and  ephe- 
merid  nymphs.  In  these,  the  rectum  is  lined  with  thousands 
of  tracheal  branches,  which  are  bathed  by  water  drawn  in  from 
behind,  and  then  expelled. 

All  these  kinds  of  respiration — cutaneous,  branchial  and 
rectal — occur  in  young  ephemerid  nymphs ;  while  mosquito 
larvcC  have  in  addition  spiracular  respiration. 

With  the  arrival  of  imaginal  life,  tracheal  gills  disappear, 
except  in  Perlidse,  and  even  in  these  insects  the  gills  are  of 
little  if  any  use. 

Marine  Insects. — Except  along  the  shore,  the  sea  is  almost 


Simulium;  A,  larva;  B, 
pupa,  showing  respira- 
tory filaments. 


ADAPTATIONS    OF    AQUATIC    INSECTS  IQI 

devoid  of  insect  life,  the  exceptions  being-  a  few  cliirononiid 
larvcC  which  lia\e  liecn  (h'edt^ed  in  deep  water,  and  fifteen 
species  of  }{alobafcs  (belong-inj^-  to  tlie  same  family  as  onr 
familiar  pond-skaters),  which  are  fonnd  en  warm  smooth  seas, 
where  they  snbsist  on  floating  animal  remains. 

Between  tide-marks  may  be  fonnd  varions  beetles  and  col- 
lemb(tlans,  which  feed  upon  organic  del)ris;  as  the  tide  rises, 
the  former  retreat,  but  the  latter  commonly  burrow  in  the  sand 
or  under  stones  and  become  submerged,  for  example  the  com- 
mon Auurida  inaritiiiia. 

Insect  Drift. — Seaweed  or  other  refuse  cast  upon  the  shore 
harbors  a  great  variety  of  insects,  especially  dipterous  larvae, 
staphylinid  scavengers  and  predaceous  Carabidre.  On  the 
shores  of  inland  ponds  and  lakes  a  similar  assemblage  of  in- 
sects may  be  found  feeding  for  the  most  part  on  the  remains 
of  plants  or  animals,  or  else  on  one  another.  During  a  strong 
wind,  the  leeward  shore  of  a  lake  is  an  excellent  collecting 
ground,  as  many  insects  are  driven  against  it.  On  the  shores 
of  the  Great  Lakes  insects  are  occasionally  cast  up  in  immense 
numbers,  forming  a  broad  windrow,  fifty  or  perhaps  a  hundred 
miles  long.  Needham  has  described  such  an  occurrence  on 
the  west  shore  of  Lake  ^Michigan,  following  a  gale  from  the 
northeast.  In  this  instance,  a  liter  of  the  drift  contained 
nearly  four  thousand  insects,  of  which  66  per  cent,  were  crick- 
ets {Nemobius),  20  per  cent.  Acridiidae,  and  the  remainder 
mostly  beetles  (CarabidcT,  Scarab?eidas.  Chrysomelidre,  Coc- 
cinellidae,  etc.).  dragon  flies,  moths,  butterflies  (Auosia, 
Picris,  etc.)  and  various  Hemiptera,  Hymenoptera  and  Dip- 
tera.  A  large  proportion  of  the  insects  were  acjuatic  forms, 
such  as  Hydrophilus,  Cyhistcr,  ZaitJia,  and  a  species  of  caddis 
fly ;  these  had  doubtless  been  carried  out  by  freshets,  while  the 
butterflies  and  dragon  flies  had  been  borne  out  by  a  strong 
wind  from  the  northwest,  after  which  all  were  driven  back  to 
the  coast  by  a  northeast  wind.  While  some  of  these  insects 
survived,  notably  CoccinellidcC,  Trichoptera.  Asilidie,  Acridi- 
idas  and  Gryllidc'e,  nearly  all  the  rest  were  dead  or  dying,  in- 


192  ENTOMOLOGY 

eluding  the  dragon  flies,  flies,  bumble  bees  and  waspsl  Fora- 
ging Carabidse  were  observed  in  large  numbers,  also  scaven- 
gers of  the  families  Staphylinidje,  Silphidse  and  Dermestidse. 

On  the  seashore  and  on  the  shores  of  the  Great  Lakes,  the 
salient  features  of  insect  life  are  essentially  the  same.  Sim- 
ilar species  occur  in  the  two  places  with  similar  biological 
relations,  on  account  of  the  general  similarity  of  environment. 

Origin  of  the  Aquatic  Habit. — The  theory  that  terrestrial 
insects  have  arisen  from  aquatic  species  is  no  longer  tenable, 
for  the  evidence  shows  that  the  terrestrial  type  is  the  more 
primitive.  Aquatic  insects  still  retain  the  terrestrial  type  of 
organization,  which  remains  unobscured  by  the  temporary  and 
comparatively  slight  adaptations  for 'an  aquatic  life.  Thus, 
the  development  of  tracheal  gills  has  involved  no  important 
modification  of  the  fundamental  plan  of  tracheal  respiration. 
It  is  significant,  moreover,  that  the  most  generalized,  or  most 
primiti\-e,  insects — Thysanura — are  without  exception  terres- 
trial. Acjuatic  insects  do  not  constitute  a  phylogenetJc  unit, 
but  represent  various  orders,  which  are  for  the  most  part  un- 
doubtedly terrestrial,  notwithstanding  the  fact  that  a  few  of 
these  orders  (Plecoptera,  Ephemerida,  Odonata,  Trichoptera) 
are  now  wholly  aquatic  in  habit.  Adaptations  for  an  aquatic 
existence  have  arisen  independently  and  often,  in  the  most 
diverse  orders  of  insects. 


CHAPTER    V 

COLOR    AND    COLORATION 

The  naturalist  distinguishes  between  the  terms  color  and 
coloration.  A  color  is  a  single  hue,  while  coloration  refers 
to  the  arrangement  of  colors. 

Sources  of  Color. — The  colors  of  insects  are  classed  as 
(i)  pigmental  {cliciiiical) ,  those  due  to  internal  pigments; 
(2)  structural  {physical),  those  due  to  structures  that  cause 
interference  or  reflection  of  light;  and  (3)  coiiibiiiation  colors 
(chciiiico-pliysical) ,  which  are  produced  in  both  ways  at  once. 

Structural  Colors. — The  iridescence  of  a  fly's  wing  and 
that  of  a  soap  bul)l)le  are  produced  in  essentially  the  same  way. 
The  wing,  however,  consists  of  two  thin,  transparent,  slightly 
separated  lamelhe.  which  diffract  white  light  into  prismatic 
rays,  the  color  differences  depending  upon  differences  in  the 
distance  between  the  two  membranes. 

The  brilliant  iridescent  hues  of  many  butterfly  scales  are  due 
to  the  diffraction  of  light  by  fine,  closely  parallel  strije  (Fig. 
92)  just  as  in  the  case  of  the  "  diffraction  gratings  "  used  by 
the  physicist,  which  consist  of  a  glass  or  metallic  plate  wath 
parallel  diamond  rulings  of  microscopic  fineness.  The  par- 
ticular color  produced  depends  in  both  cases  upon  the  distance 
between  the  striae.  Though  almost  all  lepidopterous  scales  are 
striated,  it  is  only  now  and  then  that  the  striae  are  sufficiently 
close  together  to  give  diffraction  colors.  In  a  Brazilian  species 
of  A  pat  lira  the  iridescent  scales  have  1050  strire  to  the  milli- 
meter, and  in  a  species  of  Morplw,  according  to  Kellogg,  the 
iridescent  pigmented  scales  have  1,400  striae  per  millimeter,  the 
striae  being  only  .0007  mm.  apart;  wdiile  in  some  of  the  finest 
Rowland  gratings  they  are  as  far  apart  as  .0015  mm.,  though 
numbering  1,700  per  millimeter. 

These  interference  colors  of  butterfly  scales  may  be  due.  not 
u  193 


194  ENTOMOLOGY 

only  to  surface  markings,  but  also  to  the  lamination  of  the 
scale  and  to  the  overlapping-  of  two  or  more  scales.  In  beetles 
the  metallic  blues  and  greens,  and  iridescence  in  general,  are 
often  produced  by  minute  lines  or  pits  that  diffract  the  light. 
Purely  structural  colors,  however,  are  not  so  common  as  might 
be  supposed,  according  to  Tower,  who  says,  "  The  pits  alone, 
however,  are  powerless  to  produce  any  color;  it  is  only  when 
they  are  combined  with  a  highly  reflecting  and  refractive  sur- 
face lamella  and  a  pigmented  layer  below  that  the  iridescent 
color  appears.  The  action  of  light  is  in  this  case  the  same  as 
in  the  plain  metallic  coloring,  excepting  that  each  pit  acts  as 
a  revolving  prism  to  disperse  different  wave-lengths  of  light 
in  different  directions,  and  the  combined  result  is  iridescence. 
The  existence  of  minute  pits  over  the  body  surface  is  of  com- 
mon occurrence,  but  it  is  only  wdien  they  are  combined  as 
above  that  iridescent  colors  occur." 

Silvery  white  effects  are  usually  caused  by  the  total  reflec- 
tion of  light  from  scales  or  other  sacs  that  are  filled  with  air ; 
the  same  silvery  appearance  is  given  also  by  air-filled  trachese 
and  by  the  air  bubbles  that  many  aquatic  insects  carry  about 
under  water. 

Violet,  blue-green,  coppery,  silver  and  gold  colors  are,  with 
few  exceptions,  structural  colors.      (Mayer.) 

Pigmental  Colors. — These  are  either  cuticular  or  hypo- 
dcnnal.  The  predominant  brown  and  black  colors  of  insects 
are  made  by  pigment  diffused  in  the  outer  layer  of  the  cuticula 
(Fig.  88).  Cockroaches  are  almost  white  just  after  a  moult, 
but  soon  become  brown,  and  many  beetles  change  gradually 
from  brown  to  black.  In  these  cases  it  is  apparently  signifi- 
cant that  the  cuticular  pigments  lie  close  to  the  surface  of  the 
skin,  i.  e.,  where  they  are  most  exposed  to  atmospheric 
influences.  Tower  finds,  however,  that  cuticular  colors  "  are 
not  clue  to  drying,  oxidation,  secretion,  or  like  processes,"  but 
are  due  to  "  some  katalytic  agent  or  enzyme  [formed  by  the 
hypodermis]  which,  passing  out  through  the  pore  canals, 
comes  in  contact  with  the  primary  cuticula  and  there  becomes 
the  active  factor  in  the  production  of  cuticula  colors." 


COLOR    AND    COLORATION  195 

Tlie  cuticular  pigments  are  derived,  of  course,  from  the 
underlying  hypodermis  cells,  and  these  cells  themselves,  more- 
over, usually  contain  ( i )  colored  granules  or  fatty  drops 
which  give  red,  yellow,  orange  and  sometimes  white  or  gold 
colors  as  seen  through  the  skin;  (2)  diffused  chlorophyll 
(green)  or  xanthophyll  (yellow),  taken  from  the  food  plant. 
Unlike  the  structural  colors,  which  are  persistent,  these  hypo- 
dermal  colors  often  change  after  death,  though  less  rapidly 
when  the  pigments  are  tightly  enclosed,  as  in  scales  or  hairs. 
Though  white  and  green  are  structural  colors  as  a  rule, 
they  are  due  to  pigments  in  Pieridce,  Lyc3enid?e  and  some 
Geometridcie. 

Frequently  a  color  pattern  consists  partly  of  cuticular  and 
partly  of  hypodermal  colors,  the  hypodermal  or  sub-hypoder- 
mal  color  forming  "  a  groundwork  upon  which  the  pattern  is 
cut  out  by  the  cuticular  color."  (Tower.)  Thus  in  Lcptino- 
tai'sa  dcccmlineata  the  pattern  "  is  composed  of  a  dark  cutic- 
ular pigment  upon  a  yellow  hypodermal  background." 

Combination  Colors. — The  splendid  changeable  hues  of 
Apotnra,  Eiiphva  and  other  tropical  butterflies  depend  upon 
the  fact  that  their  scales  are  both  pigmented  and  striated. 
Under  the  microscope,  certain  Apatiira  scales  are  brown  by 
transmitted  light  and  violet  by  reflected  light,  and  to  the  un- 
aided eye  the  color  of  the  wing  is  either  brown  or  violet,  ac- 
cording as  the  light  is  received  respectively  from  the  pigment 
or  from  the  striated  surfaces  of  the  scales.  According  to 
Tower,  chemico-physical  colors  "  which  are  of  exceedingly 
wide  occurrence,  are  also  the  most  brilliant  and  varied  of  all 
those  found  in  insects.  To  this  class  belong  all  metallic,  iri- 
descent, pearly,  and  translucent  colors,  as  well  as  blue,  green, 
and  violet  in  almost  every  case." 

Nature  of  Pigments. — Some  pigments  are  taken  bodily 
from  the  food ;  others  are  manufactured  indirectly  from  the 
food,  and  some  of  these  are  excretory  products. 

The  green  color  of  many  caterpillars  and  grasshoppers  is 
due  to  chlorophyll,  which  tinges  the  blood  and  shows  through 


196  ENTOMOLOGY 

the  transparent  integument.  ]\Iayer  has  found  that  scales  of 
Lepidoptera  contain  only  blood  while  the  pigment  is  forming; 
that  the  first  color  to  appear  upon  the  pupal  wings  is  a  dull 
ochre  or  drab — the  same  color  that  the  blood  assumes  when 
it  is  removed  from  the  pupa  and  exposed  to  the  air;  also  that 
pigments  like  those  of  the  wings  may  be  manufactured  artifi- 
cially from  pupal  blood.  Pierid?e  are  peculiar  in  the  nature 
of  their  pigments,  as  Hopkins  has  shown.  The  white  pigment 
of  this  family  is  uric  acid  and  the  reds  and  yellows  of  Pieris. 
Colias  and  Papilio  are  due  to  derivatives  of  uric  acid ;  the 
yellow  pigment,  termed  lepidotic  acid,  precedes  the  red  in  time 
of  appearance,  the  latter  being  probably  a  derivative  of  the 
former.  The  green  pigments  of  some  Papilionidse,  Noctu- 
idse,  Geometridc-e  and  Sphingidje  are  also  said  by  some  inves- 
tigators to  be  products  of  uric  acid,  which  in  insects  as  in  other 
animals  is  primarily  an  excretory,  or  waste,  product. 

Effects  of  Food  on  Color. — Besides  chlorophyll,  to  which 
various  caterpillars,  aphids  and  other  forms  owe  their  green 
color,  the  yellow  constituent  of  chlorophyll,  namely  xantho- 
phyll,  frequently  imparts  its  color  to  plant-eating  insects,  while 
some  phytophagous  species  are  dull  yellow  or  brown  from  the 
presence  of  tannin,  taken  from  the  food  plant.  Most  pig- 
ments, however,  are  elaborated  from  the  food  by  chemical 
processes  that  are  not  well  understood. 

Many  who  have  reared  Lepidoptera  extensively  know  that 
the  color  of  the  imago  is  influenced  by  the  character  of  the 
larval  food,  other  conditions  being  equal,  and  are  able  at  will 
to  effect  certain  color  changes  simply  by  feeding  the  larvse 
from  birth  upon  particular  kinds  of  plants.  In  this  country 
we  have  few  observations  upon  the  subject,  but  in  Europe 
the  effects  of  food  upon  coloration  have  been  ascertained  in 
the  case  of  many  species  of  Lepidoptera.  According  to  Greg- 
son,  Hybernia  defoliaria  is  richly  colored  when  fed  upon 
birch,  but  is  dull  colored  and  almost  unmarked  when  fed  on 
elm.  Pictet,  by  feeding  larvae  of  J^aucssa  urficcc  on  the  flow- 
ers instead  of  the  leaves  of  the  nettle  obtained  the  variety 


COLOR    AND    COLORATION  1 97 

known  as  wticoidcs.  T^"'ood  affects  the  color  of  the  larva  also, 
as  Poulton  found  in  the  case  of  caterpillars  of  Tryphcuna  pro- 
iiiiba,  all  from  the  same  batch  of  eggs.  When  fed  with  only 
the  white  midribs  of  cabbage  leaves,  the  larv?c  remained  almost 
white  for  a  time,  but  afterward  showed  a  moderate  amount  of 
black  pigment ;  when  fed  with  the  yellow  etiolated  heart-leaves 
or  the  dark  green  external  leaves,  however,  the  larvrc  all  be- 
came bright  green  or  brown — the  same  pigment  being  derived 
indifferently  from  etiolin  (probably  the  same  substance  as 
xanthophyll)  or  chlorophyll. 

Though  the  pigments  may  dift'er  in  color  or  amount  accord- 
ing to  the  kind  of  food,  the  color  patterns  vary  without  regard 
to  food.  Thus  CaUosamia  promctlica,  Leptinotarsa  decem- 
Uncata  (Colorado  potato  beetle),  Coccinellidae  (lady-bird 
beetles)  and  a  host  of  other  insects  exhibit  extensive  individ- 
ual variations  in  coloration  under  precisely  the  same  food  con- 
ditions. Caterpillars  of  the  same  kind  and  age  are  often  very 
dift'erently  marked  when  feeding  upon  the  same  plant;  for 
example,  Hcliothis  aniiiger  (corn  worm)  and  the  sphingid 
Dcilcphila  Uncata.  Furthermore,  striking  changes  of  colora- 
tion accompany  each  moult  in  most  caterpillars,  but  particu- 
larly those  of  butterflies,  and  these  changes  may  prove  to  have 
an  important  phylogenetic  significance.  Individual  differ- 
ences of  coloration  apart  from  those  due  to  the  direct  action 
of  food,  light,  temperature  and  other  environmental  condi- 
tions are  to  be  explained  by  heredity. 

Effects  of  Light  and  Darkness. — Sunlight  is  an  important 
factor  in  the  development  of  most  animal  pigments,  as  they 
will  not  develop  in  its  absence.  The  collembolan  Anurida 
maritima  is  white  at  hatching,  but  soon  becomes  indigo  blue, 
unless  shielded  from  sunlight,  in  which  event  it  remains  white 
until  exposed  to  the  sunlight,  when  it  assumes  the  blue  color. 
Subterranean  or  wood-boring  larvae  are  commonly  white  or 
yellow,  but  never  highly  colored.  The  most  notable  instances, 
however,  are  furnished  by  cave  insects.  These,  like  other 
cavernicolous    animals,    are    characteristically    white    or    pale 


198  ENTOMOLOGY 

from  the  absence  of  pigrnent,  if  they  hve  in  regions  of  con- 
tinual darkness,  but  have  more  or  less  pigmentation  in  propor- 
tion respectively  to  the  greater  or  less  amount  of  sunlight  to 
which  they  have  access. 

Curiously  enough,  light  often  hastens  the  destruction  of 
pigment  in  insects  that  are  no  longer  alive,  for  which  reason 
it  is  necessary  to  keep  cabinet  specimens  in  the  dark  as  much 
as  possible.  Life  is  evidently  essential  for  the  sustension  or 
renewal  of  the  pigments. 

A  chrysalis  not  infrequently  matches  its  surroundings  in 
color.  This  phenomenon  has  been  investigated  by  Poulton, 
who  has  proved  that  the  color  of  the  chrysalis  is  determined 
largely  by  the  prevalent  color  of  the  surroundings  during  the 
last  few  days  of  larval  life.  Larvae  of  Pieris  rapcu,  raised 
upon  the  same  food  plant  (all  other  conditions  being  made  as 
nearly  equal  as  possible)  produced  dark  pupae  if  kept  in  dark- 
ness for  a  few  days  just  before  pupation;  yellow  light  arrested 
the  formation  of  the  dark  pigment  and  gave  green  pupae ;  while 
light  colors  in  general  gave  light-colored  pupae.  This  color  re- 
semblance is  commonly  assumed  to  be  of  protective  value,  and 
perhaps  it  is.  Nevertheless,  it  is  a  direct  effect  of  light,  and 
does  not  need  to  be  explained  by  natural  selection,  even  though 
it  cannot  be  denied  that  natural  selection  may  have  helped  in 
its  production. 

Poulton  extended  his  studies  to  the  adaptive  coloration  of 
caterpillars  and  has  published  the  results  of  an  extensive 
series  of  experiments  which  prove  that  the  colors  of  certain 
caterpillars  also  are  directly  produced  by  the  same  colors  in 
the  surrounding  light.  Gastropacha  quercifolia,  which  always 
rests  by  day  on  the  older  wood  of  its  food  plant,  was  given 
black  twigs,  reddish  brown  sticks,  lichens,  etc.,  to  rest  upon, 
and  though  all  the  larvae  were  from  the  same  cluster  of  eggs, 
and  had  been  fed  in  the  same  way,  each  larva  gradually 
assumed  the  color  or  colors  of  its  resting  place,  resulting  in 
excjuisite  examples  of  protective  resemblance,  the  most  re- 
markable of  which  were  those  in  which  the  larvae  assumed  the 


COLOR    AND    COLORATION  199 

variegated  coloration  of  lichens.  Only  the  yonnger  larvae, 
however,  proved  to  be  susceptible  to  the  colors  of  the  environ- 
ment; unlike  those  of  Aiiiphidasis  hetnlaria,  in  which  the  older 
larvae  also  were-  sensitive  to  the  surrounding  light.  Here 
again,  natural  selection  is  unnecessary,  even  if  not  superfluous, 
as  an  explanation  of  this  kind  of  protective  coloration. 

Effects  of  Temperature. — The  amount  of  a  pigment  in  the 
wing  of  a  butterfly  depends  in  great  measure  upon  the  sur- 
rounding temperature  during  the  pupal  stage,  when  the  pig- 
ments are  forming.  Black  or  brown  spots  have  been  enlarged 
artificially  by  subjecting  chrysalides  to  cold ;  hence  it  is  probable 
that  the  characteristically  large  black  spots  on  the  under  side 
of  the  wings  of  the  spring  brood  of  our  Cyaniris  pseudargiolus 
are  simply  a  direct  effect  of  cold  upon  the  wintering  chrysal- 
ides. Similarly  the  spring  brood  (variety  marcia)  of  Phy- 
ciodes  tharos  owes  its  distinctive  coloration  to  cold,  as  Ed- 
wards has  proved  experimentally.  Lepidoptera  have  been  the 
subject  of  very  many  temperature  experiments,  some  of  which 
will  be  mentioned  presently  in  the  consideration  of  seasonal 
coloration. 

Speaking  generally,  warmth  (except  in  melanism)  tends  to 
induce  a  brightening  and  cold  a  darkening  of  coloration,  the 
darkening  being  due  to  an  increased  amount  of  black  or  brown 
pigment.  Temperature,  whether  high  or  low,  seldom  if  ever 
produces  new  pigments,  but  simply  alters  the  amount  and  dis- 
tribution of  pigments  that  are  present  already. 

Effects  of  Moisture. — Very  little  is  known  as  to  the  effects 
of  moisture  upon  coloration.  The  dark  colors  of  insular  or 
coastal  insects  as  contrasted  with  inland  forms,  and  the  pre- 
dominance of  dull  or  suffused  species  in  mountainous  regions 
of  high  humidity,  have  led  observers  occasionally  to  ascribe 
melanism  and  suffusion  to  humidity.  In  these  cases,  how- 
ever, the  possible  influence  of  low  temperature  and  other  fac- 
tors must  be  taken  into  consideration.  The  experiments  of 
Merrifield  and  of  Standfuss  showed  no  effect  of  moisture  upon 
lepidopterous  pupae. 


200  ENTOMOLOGY 

Pictet  has  recently  found,  however,  that  humidity  acting 
on  the  caterpillars  of  Vanessa  urticcu  and  V.  polychloros  has 
a  conspicuous  effect  on  the  coloration  of  the  butterflies.  Thus 
when  the  caterpillars  were  fed  for  ten  days  with  moist  leaves, 
the  resulting  iDutterflies  had  abnormal  black  markings  on  the 
wings,  and  the  same  results  followed  wdien  the  larvae  were 
kept  in  an  atmosphere  saturated  with  moisture. 

Climatal  Coloration. — The  brilliant  and  varied  colors  of 
tropical  insects  are  popularly  ascribed  to  intense  heat,  light 
and  moisture ;  and  the  dull  monotonous  colors  of  arctic  insects, 
similarly,  to  the  surrounding  climatal  conditions.  Climate 
undoubtedly  exerts  a  strong  influence  upon  coloration,  but  the 
precise  nature  of  this  influence  is  obscure  and  will  remain  so 
until  more  is  known  about  the  effects  separately  produced  by 
each  of  the  several  factors  that  go  to  make  up  what  is  called 
climate. 

The  prevalence  of  intense  and  varied  colors  among  tropical 
insects  is  doubtless  somewhat  exaggerated,  for  the  reason  that 
the  highly  colored  species  naturally  attract  the  eye  to  the  ex- 
clusion of  the  less  conspicuous  forms.  Indeed,  Wallace 
assures  us  that,  although  tropical  insects  present  some  of  the 
most  gorgeous  colors  in  the  whole  realm  of  nature,  there  are 
thousands  of  tropical  species  that  are  as  dull  colored  as  any 
of  the  temperate  regions.  Carabidse,  in  fact,  attain  their 
greatest  brilliancy  in  the  temperate  zone,  according  to  Wal- 
lace, though  butterflies  certainly  show  a  larger  proportion  of 
vivid  and  varied  colors  in  the  tropics.  Mayer  finds,  in  the 
widely  distributed  genus  Papilio,  that  200  South  American 
species  display  but  36  colors,  while  22  North  American  species 
show  17.  While  the  number  of  species  in  South  America  is 
nine  times  as  great  as  in  North  America,  the  number  of  colors 
displayed  is  only  a  little  more  than  twice  as  great ;  hence 
Mayer  concludes  that  the  richer  display  of  colors  in  the  tropics 
may  be  due  to  the  far  greater  number  of  species,  which  gives 
a  better  opportunity  for  color  sports  to  arise;  and  not  to  any 
direct  influence  of  the  climate.     Furthermore,  the  number  of 


COLOR    AND    COLORATION  201 

broods  wiiicli  occur  in  a  year  is  much  o-reater  in  the  tropics 
than  in  the  temperate  zones,  so  that  the  tropical  species  must 
possess  a  corresponchnoiy  g'reater  opportunity  to  vary. 

Albinism  and  Melanism, — These  interesting-  phenomena, 
widespread  among  the  higher  animals,  are  little  understood, 
but  appear  to  be  due  chiefly  to  temperature. 

Albiiiisiit  is  excepti(^nal  whiteness  or  paleness  of  coloration, 
and  is  due  usually  to  lack  or  deficiency  of  pigment,  but  in 
some  instances  (Pieridre)  to  the  presence  of  a  white  pigment. 

The  common  yellow  butterfly,  C olios  philodicc,  and  its  rela- 
tives, are  frequently  albinic.  Indeed,  as  Scudder  observes, 
albinism  among  butterflies  in  America  appears  to  be  confined 
to  a  few  Pieridc-e,  and  to  be  restricted  to  the  female  sex ;  it  is 
more  common  in  subarctic  and  subalpine  regions  than  in  lower 
latitudes  and  altitudes,  and  only  in  the  former  places  does  it 
include  all  the  females.  At  low  altitudes,  instead  of  appear- 
ing early  in  the  year  as  mig"ht  be  expected,  the  albinic  forms 
appear  during'  the  warmer  months. 

In  Europe  there  are  many  albinic  species  of  butterflies,  and 
they  are  by  no  means  confined  to  the  family  Pierid?e. 

Mclaiiisjii  is  unusual  blackness  or  darkness  of  coloration. 
As  to  how  it  is  produced  little  is  known,  though  warmth  is 
probably  the  most  potent  influence,  and  some  attribute  it  to 
moisture,  as  w^as  mentioned.  Pictet  obtained  partial  melan- 
ism in  Vanessa  tirticce  and  V.  polycJiIoros  by  subjecting  the 
larvae  to  moisture. 

In  warm  latitudes,  some  females  of.  our  Papilio  glaiicus 
are  blackish  brown  with  black  markings,  instead  of  being,  as 
usual,  yellow  with  black  markings.  In  the  South,  some  males 
of  the  spring  brood  of  Cyaniris  pseiidargiolus  are  partly  or 
wholly  brown  instead  of  blue. 

Seasonal  Coloration. — When  butterflies  have  more  than 
one  brood  in  a  year,  the  broods  usually  differ  in  aspect,  some- 
times so  much  that  their  specific  identity  is  revealed  only 
by  rearing  one  brood  from  another.  The  same  species  may 
exist  under  two  or  more  distinct  forms  during-  the  same  sea- 


202  ENTOMOLOGY 

son — in  other  words,  may  be  seasonally  diinorphic,  trimorphic 
or  polymorphic. 

Thus  Polygoiiia  interrogationis  has  two  forms,  fabricii  and 
umbrosa,  which  differ  not  only  in  coloration,  but  even  in  the 
form  of  the  wings  and  the  genitalia.  In  New  England  fabricii 
hibernates  and  produces  umbrosa,  as  a  rule,  while  umbrosa 
usually  yields  fabricii. 

The  little  blue  butterfly,  Cyaiiiris  pseudargiolus  (Fig.  231), 
is  polymorphic  tp  a  remarkable  degree.  In  the  high  latitudes 
of  Canada,* a  single  brood  (litcia)  occurs.  About  Boston,  the 
same  spring  brood  appears,  but  under  two  forms :  an  earlier 
variety    (liicia) ,   which   is   small,   with  large  black  markings 

Fig.  231. 


C 

Cyaniris  pseudargiolus;  A,   form  lucia;  B,   liolacea;   C,  pseudargiolus  proper. 
Natural  size. 

beneath;  and  a  later  variety  (violacea),  which  is  typically 
larger,  with  smaller  black  spots,  though  it  varies  into  the  form 
lucia.  Finally,  in  summer,  a  third  form  {pseudargiolus 
proper)  appears,  as  the  product  of  lucia  or  else  the  joint  prod- 
uct of  lucia  and  violacea,  and  this  is  still  larger,  but  the  black 
spots  are  now  faint.  In  the  warm  South,  the  spring  form  is 
violacea,  but  while  some  of  the  males  are  blue,  others  are 
melanic,  as  just  mentioned — a  dimorphic  condition  which  does 
not  occur  in  the  North.  Jlolacca  then  produces  pseudargi- 
olus, in  which,  however,  all  the  males  are  blue. 

Iphiclidcs  ajax  (Fig.  232)  is  another  polymorphic  butterfly 
whose  life  history  is  complex.  The  three  principal  varieties 
of  this  species,  known  respectively  as  marcellus,  telamonides 
and  ajax,  differ  not  only  in  coloration,  but  also  in  size  and 
form;  uiarccUus  appears  first,  in  spring;  tclaiuonidcs  appears 


COLOR    AND    COLORATION 


203 


a  little  later  (though  heforc  niarccllits  has  disappeared)  ;  and 
aja.v  is  the  summer  form ;  as  the  season  advances  the  varieties 
become  successively  larger,  with  longer  tails  to  the  hind  wings. 


Iphiclidcs  aja.v.   fLirin  tclaiiioiiiilcs,  on   flower  of  button  bush.      Reduced. 

Now  Edw^ards  submitted  chrysalides  of  the  summer  form 
ajax  to  cold  and  thereby  obtained,  in  the  same  summer,  butter- 
flies with  the  form  of  ajax  but  the  markings  of  the  spring 

Fig.  233. 


Phyciodes   fliaros;   A,    spring    form,    marcia;   B,    summer    form,    morphcus ;    under    sur- 
faces.    Natural   size. 


form  telamonidcs.      Some  of  the  chrysalides,  however,  lasted 
over  until  the  next  spring  and  then  gave  tdauwnidcs. 


204  ENTOMOLOGY 

In  PJiyciodcs  tharos  (Fig.  233)  the  spring  and  summer 
broods,  termed  respectively  marcia  and  morpheus,  were  at  first 
regarded  as  distinct  species.  In  marcia  the  hind  wings  are 
heavily  and  diffusely  marked  beneath  with  strongly  contrast- 
ing colors,  while  in  morpheus  they  are  plain  and  but  faintly 
marked.  Edwards  placed  upon  ice  eighteen  chrysalides  that 
normally  would  have  produced  morpheus;  but  instead  of  this, 
the  fifteen  imagines  that  emerged  were  all  of  the  spring  form 
marcia  and  were  smaller  than  usual.  Pupae  derived  from 
eggs  of  marcia  gave,  after  artificial  cooling,  not  morpheus, 
but  marcia  again.  The  evident  conclusion  is  that  the  distinc- 
tive coloration  of  the  spring  variety  is  brought  about  by  low 
temperature.  In  Labrador,  only  one  brood  occurs — marcia; 
in  New  York,  the  species  is  digoneutic  (two-brooded)  and  in 
West  Virginia  polygoneutic  (several-brooded). 

Extensive  temperature  experiments  upon  seasonal  dimor- 
phism in  Lepidoptera  have  been  conducted  in  Europe  by  some 
of  the  most  competent  biologists.  Weismann  found  that  pupae 
of  the  summer  form  of  Pieris  napi,  if  placed  on  ice,  disclosed 
the  darker  winter  form,  usually  in  the  same  season,  though 
sometimes  not  until  the  next  spring.  It  was  found  impossible, 
however,  to  change  the  winter  variety  into  the  summer  one 
by  the  application  of  heat.  Similar  results  have  attended  the 
important  and  much-discussed  experiments  of  Dorfmeister, 
Weismann  and  others  upon  ]'\messa  levana-prorsa  and  other 
species,  from  which  it  has  been  inferred  by  Weismann  that 
the  winter  form  is  the  primary,  older,  and  more  stable  of  the 
two  forms,  and  the  summer  form  a  secondary,  newer,  and  less 
stable  variety;  since  the  latter  form  only,  as  a  rule,  responds 
much  to  thermal  influences.  A\'eismann  argues  that,  in  addition 
to  the  direct  effect  of  temperature,  alternative  inheritance  also 
plays  an  important  part  in  the  production  of  seasonal  varieties. 
He  tries  to  show,  moreover,  that  each  seasonal  variety  is  col- 
ored in  adaptation  to  its  particular  environment  and  that  this 
adaptation  may  have  been  brought  about  by  natural  selection — 
though  he  does  not  succeed  in  this  respect. 


COLOR    AND    COLORATION  205 

In  several  instances,  local  varieties  have  been  artificially  pro- 
duced as  results  of  temperature  control.  Thus  Standfuss 
produced  in  Germany,  by  the  application  of  cold,  individuals 
of  J\Tiicssa  iirticw  Avhich  were  indistinguishable  from  the 
northern  variety  polaris;  and  from  pupa;  of  Vanessa  cardiii, 
by  warmth,  a  very  pale  form  like  that  found  in  the  tropics ; 
and,  by  cold,  a  dark  variety  similar  to  one  found  in  Lapland. 

These  investigators  and  others,  notably  Merrifield  and 
Fischer,  have  accumulated  a  considerable  mass  of  experimen- 
tal evidence,  the  interpretation  of  which  is  in  many  respects 
difficult,  involving  as  it  does,  not  merely  the  direct  effect  of 
temperature  upon  the  organism,  but  also  deep  questions  of 
heredity,  including  reversion,  individual  variation,  and  the  in- 
heritance of  accpired  characters. 

The  seasonal  increase  in  size  that  is  noticeable,  as  in  C. 
psciidargiolus  and  /.  ajax,  is  doubtless  an  expression  of  in- 
creasing metabolism  due  to  increasing  temperature.  Warmth, 
as  is  well  known,  stimulates  growth,  and  cold  has  a  dwarfing 
effect.  While  this  is  true  as  a  rule,  there  are  some  apparent 
exceptions,  however.  Thus  Standfuss  found  that  some  cater- 
]5illars  were  so  much  stimulated  by  unusual  warmth  that  they 
pupated  before  they  were  sufficiently  fed,  and  gave,  therefore, 
tmdersized  imagines.  A  moderate  degree  of  w^armth,  how- 
ever, undoubtedly  hastens  growth. 

Sexual  Coloration. — The  sexes  are  often  distinguished  by 
colorational  as  well  as  structural  differences.  Colorational 
antigcny  (this  word  signifying  secondary  sexual  differences 
of  whatever  sort)  is  most  prevalent  among  butterflies,  in 
which  it  is  the  extreme  phase  of  that  differentiation  of  orna- 
mentation for  which  Lepidoptera  are  unrivaled. 

The  male  of  Picris  protodice  (Fig.  234)  has  a  few  brown 
spots  on  the  front  wings ;  the  female  is  checkered  wdth  brown 
on  both  wings.  In  Colias  philodice  (Fig.  235)  and  C.  ciiry- 
thcinc  the  marginal  black  band  of  the  front  wings  is  sharp 
and  uninterrupted  in  the  male,  but  diffuse  and  interrupted  by 
3'ellow  spots  in  the  female.      In  the  genus  Papilio  the  sexes 


2o6 


ENTOMOLOGY 

Fig.  234, 


Picris   protodicc; 


le   left)    and    female    (on   the   right).      Natural   size. 


Fig.  235. 


are  often  distinguished  by  colorational  differences  and  in  Hes- 
periidae  the  males  often  have  an  obHque  black  dash  across  the 
middle  of  each  front  wing.  Callosainia  promethea  (Fig. 
236),  the  gypsy  moth  and  many  other  Lepidoptera  exhibit 
colorational  antigeny.  In  not  a  few  Sesiidse  the  sexes  differ 
greatly  in  coloration.  Thns  in  the 
male  of  the  peach  tree  borer  {San- 
ninoidca  exitiosa)  all  the  wings  are 
colorless  and  transparent;  while  in 
the  female  the  front  wings  are  vio- 
let and  opaque  and  the  fourth  ab- 
dominal segment  is  orange  above. 
The  same  sex  may  present  two 
types  of  coloration,  as  do  males  of 
Cyan  iris  pseudargiohis  and  females 
of  Papilio  glauciis,  already  men- 
tioned. Papilio  nicrope,  of  South 
Africa,  is  remarkable  in  having  three 
females  (Frontispiece,  Figs.  5,  7,  9, 
11)  which  are  entirely  different  in 
coloration  from  one  another  and 
from  the  male.  There  is  no  longer  any  doubt,  it  may  be 
added,  as  to  the  specific  identity  of  these  forms. 

Next  to  Lepidoptera,  Odonata  most  frequently  show  col- 
orational antigeny.     The  male  of  Calopteryx  macitlata  is  vel- 


Colias  philodice;  right  fore 
wing  of  male  (above)  and  of 
female     (below).     Natural     size. 


COLOR    AND    COLORATION 


207 


vetv  black ;  the  female  smoky,  with  a  white  ptcrostigmatal 
spot.  Among-  Coleoptera,  the  male  of  Hoplia  trifasciata  is 
grayish  and  the  female  reddish  brown ;  a  few  more  examples 
might  be  given,  though  sexual  differences  in  coloration  are 

Fig.  236. 


Callosamia  promethca;  A,  male,  clinging  to  cocoon;  B,  female.      Reduced. 

comparatively  rare  among  beetles.     Of  Hymenoptera,   some 
of  the  Tenthredinidae  exhibit  colorational  antigeny. 

Among  tropical  butterflies  there  are  not  a  few  instances  in 
which  the  special  coloration  of  the  female  is  adaptive — har- 
monizing with  the  surroundings  or  else  imitating  with  remark- 
able precision  the  coloration  of  another  species  which  is  known 


208  ENTOMOLOGY 

to  be  immune  from  the  attacks  of  birds — as  descril^ed  beyond. 
In  this  way.  as  \\'allace  sug-gests.  the  egg--laden  females  may 
escape  destruction,  as  they  shiggishly  seek  the  proper  plants 
upon  which  to  lay  their  eggs.  Here  would  be  a  fair  field  for 
the  operation  of  natural  selection. 

In  most  insects,  however,  sexual  differences  in  coloration 
are  apparently  of  no  protective  value  and  are  usually  so  trivial 
and  variable  as  probably  to  be  of  no  use  for  recognition  pur- 
poses. The  usual  statement  that  these  differences  facilitate 
sexual  recognition  is  a  pure  assumption,  in  the  case  of  insects, 
and  one  that  is  inadec|uate  in  spite  of  its  plausibility,  for  (i) 
it  is  extremely  improbable  from  our  present  knowledge  of 
insect  vision  that  insects  are  able  to  perceive  colors  except  in 
the  broadest  way.  namely,  as  masses;  (2)  the  great  majority 
of  insect  species  show  no  sexual  differences  in  coloration;  (3) 
when  colorational  antigeny  is  present  it  is  probably  unneces- 
sary, to  say  the  least,  for  sexual  recognition.  Thus,  n(jtwith- 
standing  the  marked  dissimilarity  of  coloration  in  the  two 
sexes  of  C.  proincthea,  the  males,  guided  by  an  odor,  seek  out 
their  mates  even  when  the  wings  of  the  female  have  been  am- 
putated and  male  Avings  glued  in  their  place,  as  Alayer  found. 

Hence,  when  useless,  colorational  antigeny  cannot  have 
been  developed  by  natural  selection  and  may  be  due  simply 
to  the  extended  action  of  the  same  forces  that  have  produced 
variety  of  coloration  in  general. 

Origin  of  Color  Patterns. — Tower,  who  has  written  an 
important  work  on  the  C(3lors  and  color  patterns  of  Coleop- 
tera,  finds  that  each  of  the  black  spots  on  the  pronotum  of  the 
Colorado  potato  beetle  (Fig.  237)  "  is  developed  in  connection 
with  a  muscle,  and  marks  the  point  of  attachment  of  its  fibers  to 
the  cuticula."  Thus  the  color  pattern,  in  its  origin,  is  not  neces- 
sarily useful.  This  point  is  so  important  that  we  cjuote  Tow- 
er's conclusions  in  full.  "  The  most  important  and  widely 
disseminated  of  insect  colors  are  those  of  the  cuticula  .  .  . 
these  colors  develop  as  the  cuticula  hardens,  and  appear  first, 
as  a  rule,  upon  sclerites  to  which  muscles  are  attached.      In 


COLOR    AND    COLORATION  2O9 

one  of  the  earlier  sections  of  this  paper  I  showed  that  the  pig- 
ment develops  from  Ijefore  Imckwanl  and,  approximately,  by 
segments,  excepting  that  it  may  appear  npon  the  head  and 
most  posterior  segments  simultaneously. 

"  In  ontogeny  color  appears  first,  as  a  rule,  over  the  muscles 
which  become  active  first,  or  upon  certain  sclerites  of  the  body. 
These  are  usually  the  head  muscles,  although  exceptions  are 
not  infrequent.  It  should  be  remembered  that  as  the  color 
appears  the  cuticula  hardens,  and,  considering"  that  muscles 
must  ha^■e  fixed  ends  for  their  action,  it  seems  that  there  is  a 
definite  relation  between  the  development  of  color,  the  hard- 
ening of  the  cuticula,  and  the  beginning  of  muscular  activity ; 
the  last  being  dependent  upon  the  second,  and,  incidentally, 
accompanied  by  the  first.  As  muscular  activity  spreads  over 
the  animal  the  cuticula  hardens  and  color  appears,  so  that 
color  is  nearly,  if  not  wholly,  segmentally  developed. 

"  The  relation  which  exists  between  cuticular  color  and  the 
stiffening  of  the  cuticula  is  thus  a  physiological  one,  the  cutic- 
ula not  being  able  to  harden  without  becoming  yellow  or 
brown.  \\'hat  bearing  has  this  upon  the  origin  of  color  pat- 
terns? In  the  lower  forms  of  tracheates,  such  as  the  Myria- 
pods,  colors  appear  as  segmental  repetitions  of  spots  or  pig- 
mented areas  which  mark  either  important  sclerites  or  muscle 
attachments.  On  the  abdomens  of  insects,  where  segmenta- 
tion is  best  observed,  color  appears  as  well-defined,  segmen- 
tally arranged  spots,  but  on  the  thorax  segmentation  is  ob- 
scured and  lost  upon  the  head.  Of  what  importance,  then,  is 
pigmentation?  x'Vnd  how  did  it  arise?  If  the  ontogenetic 
stages  offer  any  basis  for  phylogenetic  generalization,  we  may 
conclude  that  cuticula  color  originated  in  connection  wdth  the 
hardening  of  the  integiunent  of  the  ancestral  tracheates  as 
necessary  to  the  muscular  activity  of  terrestrial  life.  The 
primitive  colors  were  yellows,  browns  and  blacks,  correspond- 
ing well  with  the  surroundings  in  which  the  first  terrestrial 
insects  are  supposed  to  have  lived.  The  color  pattern  was  a 
segmental  one,  showing  repetition  of  the  same  spots  upon  suc- 
cessive segments,  as  upon  the  abdomen  of  Coleoptera. 
'5 


2  10  ENTOMOLOGY 

"  So  firmly  have  these  characters  become  ingrained  in  the 
tracheate  series,  and  so  important  is  this  relation  of  the  hard- 
ening of  the  cuticula  to  the  musculature  and  to  the  formation 
of  body  sclerites,  that  even  the  most  specialized  forms  show 
this  primitive  system  of  coloration;  and,  although  there  may 
be  spots  and  markings  which  have  no  connection  with  it,  still 
the  chief  color  areas  are  thus  closely  associated." 

Development  of  Color  Patterns. — Although  the  causes  of 
coloration  are,  for  the  most  part,  obscure,  it  is  possible,  never- 
theless, to  point  out  certain  paths  along  which  coloration  ap- 
pears to  have  developed.  These  paths  have  been  determined 
by  the  comparison  of  color  patterns  in  kindred  groups  of  in- 
sects and  the  study  of  colorational  variations  in  adults  of  the 
same  species.  The  development  of  coloration  in  the  individ- 
ual, however,  has  as  yet  received  but  little  attention — excepting 
the  excellent  studies  of  Mayer  and  of  Tower.  Butterflies, 
moths  and  beetles  have  naturally  been  preferred  by  most  stu- 
dents of  the  subject. 

The  most  primitive  colors  among  moths  are  uniform  dull 
yellows,  browns  and  drabs — the  same  colors  that  the  pupal 
blood  assumes  when  it  is  dried  in  the  air.  These  simple  col- 
ors prevail  on  the  hind  wings  of  most  moths  and  on  the  less 
exposed  parts  of  the  wings  of  highly  colored  butterflies.  The 
hind  wings  of  moths  are,  as  a  rule,  more  primitively  colored 
than  the  front  ones  because,  as  Scudder  says,  "  all  dififeren- 
tiation  in  coloring  has  been  greatly  retarded  by  their  almost 
universal  concealment  by  day  beneath  the  overlapping  front 
wings."  Exceptions  to  this  statement  are  found  in  Geomet- 
ridae  and  such  other  moths  as  rest  with  all  the  wings  spread. 
"  In  such  hind  wings  we  find  that  the  simplest  departure  from 
uniformity  consists  in  a  deepening  of  the  tint  next  the  outer  mar- 
gin of  the  wing;  next  we  have  an  intensification  of  the  deeper 
tint  along  a  line  parallel  to  the  margin  ;  it  is  but  a  step  from  this 
condition  to  a  distinct  line  or  band  of  dark  color  parallel  to 
the  margin.  Or  the  marginal  shade  may,  in  a  similar  way, 
break  up  into  two  or  more  transverse  and  parallel  submarginal 


COLOR    AND    COLORATION  2  I  I 

lines,  a  very  common  style  of  ornamentation,  especially  in 
moths.  Or,  again,  starting-  with  the  snbmarg-inal  shade,  this 
may  send  shoots  or  tongiies  of  dark  color  a  short  distance 
toward  the  base,  giving-  a  serrate  inner  border  to  the  marginal 
shade;  when  now  this  breaks  np  into  one,  two,  or  more  lines 
or  narrow  stripes,  these  stripes  become  zigzag,  or  the  inner 
ones  may  be  zigzag,  while  the  outer  ones  are  plain — a  very 
common  phenomenon. 

"  A  basis  such  as  this  is  sufficient  to  account  for  all  the  modi- 
fications of  simple  transverse  markings  which  adorn  the  wings 
of  Lepidoptera." 

Briefly,  one  or  more  liands  may  break  up  into  spots  or  bars, 
the  breaks  occurring  either  between  the  veins  or,  more  com- 
monly, at  the  veins ;  and  in  the  latter  event,  short  bars  or  more 
or  less  quadrate  or  rounded  spots  arise  in  the  interspaces. 
From  simple  round  spots  there  may  develop,  as  Darwin  and 
others  have  shown,  many-colored  eye-like  spots,  or  ocelli. 

]\Iayer  gives  the  following  laws  of  color  pattern  :  "  (a)  Any 
spot  found  upon  the  wing  of  a  butterfly  or  moth  tends  to  be 
bilaterally  symmetrical,  both  as  regards  form  and  color;  and 
the  axis  of  symmetry  is  a  line  passing  through  the  center  of 
the  interspace  in  which  the  spot  is  found,  parallel  to  the  longi- 
tudinal nervures.  (b)  Spots  tend  to  appear  not  in  one  inter- 
space only,  but  in  homologous  places  in  a  row  of  adjacent 
interspaces,  (c)  Bands  of  color  are  often  made  by  the  fusion 
of  a  row  of  adjacent  spots,  and,  conversely,  chains  of  spots  are 
often  formed  by  the  breaking  up  of  bands,  (d)  When  in 
process  of  disappearance,  bands  of  color  usually  shrink  away 
at  one  end.  (c)  The  ends  of  a  series  of  spots  are  more  vari- 
able than  the  middle.  (/)  The  position  of  spots  situated  near 
the  outer  edges  of  the  wing  is  larg'ely  controlled  by  the  wing- 
folds  or  creases." 

These  results  have  Ijeen  arrived  at  chiefly  by  the  study  of 
the  variations  presented  by  color  patterns. 

Variation  in  Coloration. — It  is  safe  to  say  that  no  two 
insects  are  colored  exactly  alike.     Some  species,  however,  are 


m 


10 


12 


13 


14 


^>:uu 


16 


Colorational    variations   of    the   pronotum    of   the    Colorado    potato    beetle,    Leptinotar 
deccmlineata. 


Fig.  238. 


18 


Elytral  color  patterns  of  species  of  Cicindela.  1-8  illustrate  reduction  of  dark  area; 
^14,  extension  of  dark  area;  15,  16,  formation  of  longitudinal  vitta;  17,  18,  linear 
extension  of  markings.  I,  C.  vulgaris;  2,  generosa;  3,  generosa;  4,  pamphila;  5,  lim- 
bata;  6,  togata;  7,  gratiosa;  8,  canosa;  g,  tenuisignata;  10,  marginipennis;  11,  hentzii; 
12,  sexguttata;  13,  hemorrhagica;  14,  splendida;  15,  imperfecta;  16,  lemniscata; 
17,  gabbii;  18,  sanlcyi. — After  Horn,   from   Entomological  News.  ^21^) 


214  ENTOMOLOGY 

far  more  variable  than  others.  Catocala  ilia,  for  example, 
occurs  under  more  than  fifty  varieties,  each  of  which  might 
be  given  a  distinctive  name,  were  it  not  for  the  fact  that  these 
varieties  run  into  one  another.  One  may  examine  hundreds 
of  potato  beetles  (L.  decemlincata)  without  finding  any  two 
that  have  precisely  the  same  pattern  on  the  pronotum.  The 
range  of  this  variation  in  this  species  is  partially  indicated  in 
Fig.  237,  and  that  of  Cicindela  in  Fig.  238. 

Individuals  of  Cicindela  vary  in  pattern  in  a  few  definite 
directions,  and  the  patterns  that  characterize  the  various  spe- 
cies appear  to  be  fixations  of  individual  variations.  In  the 
words  of  Dr.  Horn:  "  (i)  The  type  of  marking  is  the  same 
in  all  our  species.  (2)  Assuming  a  well-marked  species  {vul- 
garis, Fig.  238,  i)  as  a  central  type,  the  markings  of  other 
species  vary  from  that  type,  {a)  by  a  progressive  spreading 
of  the  white,  (&)  by  a  gradual  thinning  or  absorption  of  the 
white,  (c)  by  a  fragmentation  of  the  markings,  {d)  by  linear 
supplementary  extension.  (3)  Many  species  are  practically 
invariable  (/.  e.,  the  individual  variations  are  small  in  amount 
as  compared  with  those  in  other  species).  These  fall  into  two 
series :  (a)  those  of  the  normal  type,  as  vulgaris,  hirticollis 
and  tenuisignata;  (b)  those  in  which  some  modification  of  the 
type  has  become  permanent,  probably  through  isolation,  as 
marginipennis,  to  gala  and  lemniscata.  (4)  Those  species 
which  vary  do  so  in  one  direction  only."  New  types  of  pat- 
tern, of  specific  value,  appear  to  have  arisen  by  the  isolation 
and  perpetuation  of  individual  variations. 

Variations  in  general  fall  into  two  classes:  continuous  {in- 
dividual variations)  and  discontinuous  {sports).  The  former 
are  always  present,  are  slight  in  extent  and  intergrade  with 
one  another;  they  are  distributed  symmetrically  about  a  mean 
condition.  The  latter  are  occasional,  of  considerable  extent 
and  sharply  separated  from  the  normal  condition. 

Replacements.- — Examples  of  the  replacement  of  one  color 
by  another  are  familiar  to  all  collectors.  The  red  of  Vanessa 
atalanta  and  Coccinellidje  may  be  replaced  by  yellow.     These 


COLOR    AND    COLORATION  21  5 

two  colors  in  many  butterflies  and  l:)eetles  are  due  to  pig^ments 
that  are  closely  related  to  each  other  chemically.  Thus  in  the 
chrysomelid  Melasonia  lapponica  the  beetle  at  emergence  is 
pale  but  soon  becomes  yellow  with  black  markings,  and  after 
several  hours,  under  the  influence  of  sunlight,  the  yellow 
changes  to  red  ;  the  change  may  be  prevented,  however,  by  keep- 
ing the  beetle  in  the  dark.  After  death,  the  red  fades  back 
through  orange  to  yellow,  especially  as  the  result  of  exposure 
to  sunlight.  Yellow  in  place  of  red,  then,  may  Ije  attributed 
to  an  arrested  development  of  pigment  in  the  living  insect  and 
to  a  process  of  reduction  in  the  dead  insect,  metabolism  having 
ceased. 

Yellow  and  green  are  similarly  related.  The  stripes  of 
Pa-cilocapsiis  lincatits  are  yellow  before  they  become  green,  and 
after  death  fade  back  to  yellow.  As  the  green  pigment  in  most, 
if  not  all,  phytophagous  insects  is  chlorophyll,  these  color 
changes  are  probably  similar  to  those  that  occur  in  leaves. 
Leaves  grown  in  darkness  are  yellow,  from  the  presence  of  etio- 
lin,  and  do  not  turn  green  until  they  are  exposed  to  sunlight  (or 
electric  light),  without  which  chlorophyll  does  not  develop; 
and  as  metabolism  ceases,  chlorophyll  disintegrates,  as  in 
autumn,  leaving  its  yellow  constituent,  xanthophyll,  which  is 
very  likely  the  same  substance  as  etiolin. 

Cicindela  sexguttata  and  Calosoma  scrutator  are  often  blue 
in  place  of  green.  Here,  however,  these  colors  are  structural, 
and  their  variations  are  to  be  attributed  to  slight  differences  in 
the  spacing  of  the  surface  elevations  or  depressions. 

Green  grasshoppers  occasionally  become  pink  toward  the 
close  of  summer.  No  explanation  has  been  offered  for  this 
phenomenon,  though  it  may  be  remarked  that  when  grasshop- 
pers are  killed  in  hot  water  the  normal  green  pigment  turns  to 
pink. 

These  changes  of  color  are  apparently  of  no  use  to  the  insect, 
being  merely  incidental  effects  of  light,  temperature  or  other 
inorganic  influences. 


CHAPTER    VI 

ADAPTIVE   COLORATION 

Protective  Resemblance. — Every  naturalist  knows  of 
many  animals  that  tend  to  escape  detection  by  resembling  their 
surroundings.  This  phenomenon  of  protective  reseinhlancc 
is  richly  exemplified  by  insects,  among  which  one  of  the  most 
remarkable  cases  is  furnished  by  the  Kalliina  butterflies,  espe- 
cially K.  inachis  of  India  and  K.  paraklcta  of  the  Malay  Archi- 
pelago.    The  former  species  (Fig.  239)  is  conspicuous  when 

Fig.  239. 


A,   upper    surface; 


',    with    wings   closed,    showing    resemblance   to    a 
leaf.     X  i. 


on  the  wing;  its  bright  colors,  however,  are  confined  to  the 
upper  surfaces  of  the  wings,  and  when  these  are  folded  to- 
gether, as  in  repose,  the  insect  resembles  to  perfection  one  of 
the  dead  leaves  among  which  it  is  accustomed  to  hide.  The 
form,  size  and  color  of  the  leaf  are  accurately  reproduced,  the 
petiole  being  simulated  by  the  tails  of  the  wings.  Two  paral- 
lel  shades,   one  light   and  one   dark,   represent,   respectively, 

216 


ADAPTIVE    COLORATIOX 


217 


the  illuminated  and  the  shaded  side  of  a  mid-rib.  and  the  side- 
veins  as  well  are  imitated  ;  there  are  even  small  scattered  black 
spots  resembling-  those  made  on  the  leaf  by  a  species  of 
fungus.  Furthermore,  the  butter tly  ha])itually  rests,  not 
among  green  leaves,  where  it  would  be  conspicuous,  but  among 
leaves  with  wdiich  it  har- 

,  .  Vu;.   240. 

monizes  ni  coloration. 
Notwithstanding  a  recent 
discussion  as  to  whether 
it  usually  rests  in  pre- 
cisely the  same  position 
as  a  leaf,  this  insect  cer- 
tainly deceives  experi- 
enced entomologists  and 
presumably  eludes  birds 
and  other  enemies  by 
means  of  its  deceptive 
coloration. 

Some  of  the  tropical 
Phasmidse  counterfeit 
sticks,  green  leaves,  or 
dead  leaves  with  minute 
accuracy.  Our  common 
phasmids,  Diaphcrorncra 
fcuiorata  and  veliei  (Fig. 
240),  are  well  known  as 
"  stick  insects  "  ;  indeed, 
it  is  not  necessary  to  go 
beyond  the  temperate  zone 
to  find  plenty  of  examples 
of  protective  resemblance.  Geometrid  caterpillars  imitate  twigs, 
holding  the  body  stiffly  from  a  branch  and  frequently  reprodu- 
cing the  form  and  coloration  of  a  twig  with  striking  exactitude ; 
and  the  moths  of  the  same  family  are  often  colored  like  the 
bark  against  which  they  spread  their  wings.  Even  more  per- 
fectly do  the  Catocala  moths  resemble  the  bark  upon  which 


Diapheromcra  relic 


Natural   size. 


2l8 


ENTOMOLOGY 


they  rest  (Fig-.  241),  with  their  conspicuous  and  usually  showy 
hind  wings  concealed  under  the  protectively  colored  front 
wings.  The  caterpillars  of  Basilarchia  archippus  and  Pa- 
pilio  thoas,  as  well  as  other  larvse  and  not  a  few  moths, 
resemble  closelv  the  excrements  of  birds.     Numerous  grass- 


FiG.  241 


Catocala  lacrymosa;  A,  upper  surface;  B,  with 
Reduced. 


igs  closed,   and  resting  on  bark. 


eating  caterpillars  are  striped  with  green,  as  is  also  a  sphingid 
species  (Ellcina  harrisii)  that  lives  among  pine  needles.  The 
large  green  sphinx  caterpillars  perhaps  owe  their  inconspicu- 
ousness  partly  to  their  oblique  lateral  stripes,  which  cut  a  mass 
of  green  into  smaller  areas.  The  caterpillar  of  Schizura 
ipoiiKrcc  (Fig.  242),  which  is  green  with  brown  patches,  rests 


ADAPTIVE    COLORATION 


219 


for  hours  along"  the  eaten  or  torn  edge  of  a  basswood  leaf,  in 
which  position  it  bears  an  extremely  deceptive  resemblance  to 
the  partially  dead  border  of  a  leaf.  The  weevils  that  drop  to 
the  ground  and  remain  immovable  are  often  indistinguishable 

Fig.  242. 


Caterpillar  of  ScliKitni  ipouia-a:  clinging  to   a   torn  leaf.      Natural   size. 

to  the  collector  on  account  of  their  likeness  to  bits  of  soil  or 
little  pebbles.  Everyone  has  noticed  the  extent  to  which  some 
of  the  grasshoppers  resemble  the  soil  in  color;  Triiiicrotropis 
maritima  is  practically  invisible  against  the  gray  sand  of  the 
seashore  or  other  places  to  which  it  restricts  itself;  and  Dis- 
sostevra  Carolina,  which  varies  greatly  in  color,  ranging  from 
ashy  gray  to  yellowish  or  to  reddish  brown,  is  commonly  found 
on  soil  of  its  own  color. 

Adventitious  Resemblance. — If,  instead  of  hastily  ascrib- 
ing all  cases  apparently  of  protective  resemblance  to  the  action 
of  natural  selection,  one  inquires  into  the  structural  basis  of 
the  resemblance  in  each  instance,  it  is  found  that  some  cases 
can  be  explained,  with(.)ut  the  aid  of  natural  selection,  as  being 


220  ENTOMOLOGY 

direct  effects  of  food,  light  or  other  primary  factors.  Such  cases, 
then,  are  in  a  sense  accidental.  For  example,  many  inconspic- 
uous green  insects  are  green  merely  because  chlorophyll  from 
the  food-plant  tinges  the  blood  and  shows  through  the  skin. 
If  it  be  argued  that  natural  selection  has  brought  about  a  thin 
and  transparent  skin,  it  may  be  replied  that  the  skin  of  a  green 
caterpillar  is  by  no  means  exceptional  in  thinness  or  trans- 
parency. Moreover,  many  leaf-mining  caterpillars  are  green, 
simply  because  their  food  is  green  ;  for,  living  as  they  do  within 
the  tissues  of  leaves,  and  surrounded  by  chlorophyll,  their  own 
green  color  is  of  no  advantage,  but  is  merely  incidental. 

Ag'ain,  in  the  "  protectively "  colored  chrysalides  experi- 
mented upon  by  Poulton,  their  color  was  directly  influenced 
by  the  prevailing  color  of  the  light  that  surrounded  the  larva 
during  the  last  few  days  before  pupation.  Of  course,  it  is 
conceivable  that  natural  selection  may  have  preserved  such  in- 
dividuals as  were  most  responsive  to  the  stimulus  of  the  sur- 
rounding-  light ;  nevertheless  the  fact  remains  that  these  resem- 
blances do  not  demand  such  an  explanation,  which  is,  in  other 
words,  superfluous. 

Indeed,  a  great  many  of  the  assumed  examples  of  "protec- 
tive resemblance  "  are  very  far-fetched.  On  the  other  hand, 
when  the  resemblance  is  as  specific  and  minutely  detailed  as  it 
is  in  the  Kallima  butterflies — where,  moreover,  special  instincts 
are  involved — the  phenomenon  can  scarcely  be  due  to  chance ; 
the  direct  and  uncombined  action  of  such  factors  as  food  or 
light  is  no  longer  sufticient  to  explain  the  facts — although  these 
and  other  factors  are  undoubtedly  important  in  a  primary,  or 
fundamental,  way.  Here  natural  selection  becomes  useful,  as 
enabling  us  to  understand  how  original  variations  of  structure 
and  instinct  in  favorable  directions  may  have  been  preserved 
and  accumulated  until  an  extraordinary  degree  of  adaptation 
has  been  attained. 

Value  of  Protective  Resemblance. — The  popular  opinion 
as  to  the  efficiency  of  protective  resemblances  is  undoubtedly 
an  exaggerated  one,  owing  mainly  to  the  false  assumption  that 


ADAPTIVE    COLORATION  221 

the  senses  of  the  Ic^wcr  animals  are  C()-extensi\-e  in  range 
with  our  own.  As  a  matter  of  fact,  l)ir(ls  detect  insects  with 
a  facihty  far  superior  to  that  of  man,  and  destroy  them  hy 
the  wholesale,  in  spite  of  protective  coloration.  Thus,  as 
Judd  has  ascertained,  no  less  than  three  hundred  species  of 
birds  feed  ui)on  protectively  colored  g-rasshopi)ers,  which  they 
destrov  in  immense  numbers,  and  more  than  twenty  species 
prey  upon  the  twig-like  geometrid  larvae ;  while  the  weevils 
that  look  like  particles  of  soil,  and  the  green-striped  caterpillars 
that  assimilate  with  the  surrounding"  foliage  are  constantly  to 
be  found  in  the  stomachs  of  birds. 

After  all,  however,  protective  resemblance  may  be  regarded 
as  advantageous  upon  the  whole,  even  if  it  is  inefTectual  in 
thousands  of  instances.  An  adaptation  may  be  successful 
even  if  it  does  fall  short  of  perfection;  and  it  should  be  borne 
in  mind  that  the  evolution  of  protective  resemblances  among 
insects  has  probably  been  accompanied  on  the  part  of  birds  by 
an  increasing  ability  to  discriminate  these  insects  from  their 
surroundings. 

Warning  Coloration. — In  strong  contrast  to  the  protec- 
tively colored  species,  there  are  many  insects  which  are  so 
vividly  colored  as  to  be  extremely  conspicuous  amid  their  nat- 
ural surroundings.  Such  are  many  Hemiptera  (Lygcuus, 
Miirgantia),  Coleoptera  {Nccroplionis,  Lampyridae,  Coccinel- 
lidc-e,  Chrysomelidae),  Hymenoptera  (Mutillidae,  Vespidse), 
and  numerous  caterpillars  and  butterflies.  Conspicuous  col- 
ors, being  frecjuently — though  not  always — associated  with 
c|ualities  that  render  their  possessors  unpalatable  or  offensive 
to  birds  or  other  enemies,  are  advantageous  if,  by  insuring 
ready  recognition,  they  exempt  their  owners  from  attack. 

Efficiency  of  Warning  Colors. — Owing  to  much  disagree- 
ment as  to  the  actual  value  of  "  warning  "  colors,  several  in- 
vestigators have  made  many  observations  and  experiments 
upon  the  subject.  Tests  made  by  offering  various  conspicu- 
ous insects  to  birds,  lizards,  frogs,  monkeys  and  other  insec- 
ti^'orous  animals  have  given  diverse  results,  according  to  cir- 


222  ENTOMOLOGY 

cumstances.  Thus,  one  gaudy  caterpillar  is  refused  by  a  cer- 
tain bird,  at  once,  or  else  after  being  tasted,  but  another  and 
equally  showy  caterpillar  is  eaten  without  hesitation.  Or,  an 
insect  at  first  rejected  may  at  length  be  accepted  under  stress 
of  hunger ;  or  a  warningly  colored  form  disregarded  by  some 
animals  is  accepted  by  others.  Moreover,  some  of  the  experi- 
ments with  captive  insectivorous  animals  are  open  to  objection 
on  the  score  of  artificiality. 

Nevertheless,  from  the  data  now  accumulated,  there  emerge 
some  conclusions  of  definite  value.  Frank  Finn,  whose  con- 
clusions are  quoted  beyond,  has  foifnd  in  India  that  the  con- 
spicuous colors  of  some  butterflies  (Danainae,  Acrcua  violcc, 
Delias  eucharis,  Papilio  anstolochice)  are  probably  effective 
as  "  warning  ''  colors.  Marshall  found  in  South  Africa  that 
mantids,  which  would  devour  most  kinds  of  butterflies,  includ- 
ing warningly  colored  species,  refused  Acrcea,  which  appeared 
to  be  not  only  distasteful  but  even  unwholesome;  Acrcea  is 
eaten,  however,  by  the  predaceous  Asilidse,  which  feed  indis- 
criminately upon  insects — for  example,  beetles,  dragon  flies  and 
even  stinging  Hymenoptera.  The  masterly  studies  of  Mar- 
shall and  Poulton  strongly  support  the  general  theory  of  warn- 
ing coloration. 

In  this  country,  much  important  evidence  upon  the  subject 
has  been  obtained  by  Dr.  Judd  from  an  extensive  examination 
of  the  stomach-contents  of  birds,  supplemented  by  experiments 
and  field  observations.  Judd  says  that  Miirgantia  histrionica 
and  other  large  showy  bugs  are  usually  avoided  by  birds ;  that 
the  showy,  ill-flavored  Coccinellidss,  and  Chrysomelidas  such 
as  the  elm  leaf  beetle,  Diabrotica,  and  Leptinotarsa  {Dory- 
phora) ,  possess  comparative  immunity  from  birds ;  and  that 
Macrodacfyliis,  Chauliogiiathus  and  Cyllcne  are  highly  exempt 
from  attack.  Such  cases,  he  adds,  are  comparatively  few 
among  insects,  however,  and  in  general,  warning  colors  are 
effective  against  some  enemies  but  ineffective  against  others. 

Generally  speaking,  hairs,  stings  and  other  protective  de- 
vices are  accompanied  by  conspicuous  colors — though  there 


ADAPTIVE    COLORATION  2  23 

are  many  exceptions  to  this  rnle.  These  warnino-  colors,  how- 
ever, fail  to  accomplish  their  snpposed  purpose  in  the  follow- 
ing- instances,  given  by  Juckl.  Taking  insects  that  are  thought 
to  be  protected  by  an  offensive  odor  or  a  disagreeable  taste : 
Heteroptera  in  general  are  eaten  by  all  insectivorous  birds,  the 
squash  bug  by  hawks  and  the  pentatomids  by  many  birds ; 
among  Carabid.e  with  their  irritating  fluids,  Harpalus  caligi- 
nosiis  and  poiiisyk'aniciis  are  food  for  the  crow,  catbird,  robin 
and  six  others;  Carabits  and  Calosoiiia  are  relished  by  crows 
and  blackbirds;  Silphid^e  are  taken  by  the  crow,  loggerhead 
shrike  and  kingbird ;  and  Leptiiiotorsa  dcceinlineata  is  eaten 
by  at  least  six  kinds  of  birds  :  wood  thrush,  rose-breasted  gros- 
beak, quail,  crow,  cuckoo  and  catbird.  Of  hairy  and  spiny  cat- 
erpillars, Arctiid?e  are  eaten  by  the  robin,  bluebird,  catbird, 
cuckoo  and  others ;  the  larvae  of  the  .gypsy  moth  are  food  for 
the  blue-jay,  robin,  chickadee,  Baltimore  oriole  and  many 
others  [thirty-one  birds,  in  Massachusetts]  ;  and  the  spiny 
caterpillars  of  Vanessa  antiopa  are  taken  by  cuckoos  and  ori- 
oles. Of  stinging  Hymenoptera,  bumble  bees  are  eaten  by  the 
bluebird,  blue-jay  and  two  flycatchers ;  the  honey  bee.  by  the 
wood  pewee,  phoebe,  olive-sided  flycatcher  and  kingbird; 
Andrena  by  many  birds,  and  Vespa  and  Polistes  by  the  red- 
bellied  woodpecker,  kingbird,  and  yellow-bellied  flycatcher. 

These  facts  by  no  means  invalidate  the  general  theory,  but 
they  do  show  that  "  disagreeable  "  qualities  and  their  associ- 
ated color  signals  are  of  little  or  no  avail  against  some  enemies. 
The  weight  of  evidence  favors  the  theory  of  warning  colora- 
tion in  a  qualified  form.  A\'hile  cxDnspicuous  colors  do  not 
ahvays  exempt  their  owners  from  destruction,  they  frequently 
do  so,  by  advertising  disagreeable  attributes  of  one  sort  or 
another. 

The  evolution  of  warning  coloration  is  explained  by  natural 
selection ;  in  fact,  we  have  no  other  theory  to  account  for  it. 
The  colors  themselves,  however,  must  have  been  present  before 
natural  selection  could  begin  to  operate;  their  origin  is  a  ques- 
tion quite  distinct  from  that  of  their  subsequent  preservation. 


2  24 


ENTOMOLOGY 


Protective  Mimicry. — This  interesting  and  highly  involved 
phenomenon  is  a  special  form  of  protective  resemblance  in 
which   one   species   imitates   the   appearance   of   another   and 

Fig.  243. 


A,  Anosia  plc.vil^piis,  the  "  model 


ilarcliia  architf's,  the  "  mimic. 


better  protected  species,  thereby  sharing  its  immunity  from 
destruction.  Though  it  attains  its  highest  development  in  the 
tropics,  mimicry  is  well  illustrated  in  temperate  regions.  A 
familiar  example  is  furnished  by  Basilarchia  archippiis  (Fig. 
243,  B) ,  which  departs  widely  from  the  prevailing  dark  colora- 
tion of  its  p-enus  to  imitate  the  milkweed  buttertiv,  Anosia 


ADAPTIVE    COLORATION 


!25 


plcxippus.  The  latter  species,  or  "  model,"  appears  to  be  un- 
molested l)y  birds,  and  the  former  species,  or  "  mimic,"  is 
thought  to  secure  the  same  exemption  from  attack  by  being 
mistaken  for  its  unpalatable  model.  The  common  drone-fly, 
Eristdlis  tciiax  ( I'ig.  244,  B)  mimics  a  honey  bee  in  form,  size, 

ViG.  244. 


Protective   mimicry. 


A,   drone   bee,   Apis  mellifcra;  B,    drone   fly,   Erislalis   teiiax. 
Natural   size. 


coloration  and  the  manner  in  which  it  buzzes  about  flowers, 
in  company  with  its  model ;  it  does  not  decei^•e  the  kingbird 
and  the  flicker,  however.  Some  Asilidx  are  remarkably  like 
bumble  bees  in  superficial  appearance  and  certain  Syrphus  flies 
mimic  wasps  with  more  or  less  success.  The  beetle  Casnonia 
bears  a  remarkable  resemblance  to  the  ants  with  which  it  lives. 
The  classic  cases  are  those  of  the  Amazonian  Heliconiidse 
and  Pieridae,  in  which  mimicry  was  first  detected  by  Bates. 
The  Heliconiidas  (Frontispiece,  Fig.  i)  are  abundant,  vividly 
colored  and  eminently  free  from  the  attacks  of  birds  and  other 


and  taste.  Some  of  the  Pierid?e — a  family  fundamentally  dif- 
ferent from  Heliconiidse — imitate  (Frontispiece,  Fig.  2)  the 
protected  HeliconiidcC  so  successfully,  in  coloration,  form  and 
flight,  that  while  other  Pieridse  are  preyed  upon  by  many  foes, 
the  mimicking  species  tend  to  escape  attack. 

The  family   Heliconiidse,   referred  to  by   Bates,   comprised 
what  are  now  known  as  the  subfamilies   Heliconiin?e,   Itho- 
miinre  and  Danaina? ;  similarly,  Pieridre  and  Papilionidse  are 
16 


2  26  ENTOMOLOGY 

now  often  termed  respectively  Pierinae  and  Papilioninae. 
Ithomiinse  are  mimicked  also  by  Papilioninae  and  by  moths  of 
the  families  Castniidse  and  Pericopidae. 

The  discoveries  of  Bates  in  tropical  South  America  were 
paralleled  and  supported  by  those  of  \\'allace  in  India  and  the 
Malay  Archipelago  (where  Danainae  are  the  chief  "  models  "), 
and  of  Trimen  in  South  Africa  (where  Acrseinae  and  Danain?e 
serve  as  models).  Trimen  discovered  a  most  remarkable  case, 
in  which  three  species  of  Danainae  are  mimicked,  each  by  a 
distinct  variety  of  the  female  of  Papilio  mcropc  (Frontispiece, 
Fig-s.  5-11). 

So  much  for  that  kind  of  mimicry — but  how  is  the  following 
kind  to  be  explained?  The  Ithomiinas  of  the  i\mazon  valley 
have  the  same  form  and  colorationas  the  Hehconiinse  (Frontis- 
piece, Figs.  I,  4),  but  the  Ithomiinse  themselves  are  already 
highly  protected.  The  answer  is  that  this  resemblance  is  of 
advantage  to  both  groups,  as  it  minimizes  their  destruction  by 
birds — these  having  to  learn  but  one  set  of  warning  signals 
instead  of  two.  This  is  the  essence  of  Aliiller's  famous  expla- 
nation, which  will  presently  be  stated  with  more  precision. 
There  are  two  kinds  of  mimicry,  then :  ( i )  the  kind  described 
by  Bates,  in  which  an  edible  species  obtains  security  by  coun- 
terfeiting the  appearance  of  an  inedible  species;  (2)  that  ob- 
served by  Bates  and  interpreted  by  ]\Iuller,  in  which  both 
species  are  inedible.  These  two  kinds  are  known  respectively 
as  Batesian  and  ]\Iullerian  mimicry,  though  some  writers  prefer 
to  limit  the  term  mimicry  to  the  Batesian  type. 

Wallace's  Rules. — The  chief  conditions  under  which  mimi- 
cry occurs  have  been  stated  by  Wallace  as  follows : 

"  I.  That  the  imitative  species  occur  in  the  same  area  and 
occupy  the  very  same  station  as  the  imitated. 

"  2.  That  the  imitators  are  always  the  more  defenceless. 

''  3.  That  the  imitators  are  always  less  numerous  in  indi- 
viduals. 

"  4.   That  the  imitators  differ  from  the  bulk  of  their  allies. 

"  5.  That  the  imitation,  however  minute,   is  external  and 


ADAPTIVE    COLORATION  22/ 

visible  only,  never  extending  to  internal  characters  or  to  such 
as  do  not  affect  the  external  appearance." 

These  rules  relate  chiefly  to  the  Batesian  form  of  mimicry 
and  need  to  be  altered  to  apply  to  the  Miillerian  kind. 

The  first  criterion  given  by  Wallace  is  evidently  an  essential 
one  and  it  is  sustained  by  the  facts.  It  is  also  true  that  mimic 
and  model  occur  usually  at  the  same  time  of  year ;  Marshall 
found  many  new  instances  of  this  in  South  Africa.  In  some 
cases  of  mimicry,  strange  to  say,  the  precise  model  is  unknown. 
Thus  some  Nymphalid?e  diverge  from  their  relatives  to  mimic 
the  Euploeina?,  though  no  particular  model  has  been  found. 
In  such  instances,  as  Scudder  suggests,  the  prototype  may 
exist  without  having  been  found;  may  have  become  extinct; 
or  the  species  may  have  arrived  at  a  general  resemblance  to 
another  group  without  having  as  yet  acquired  a  likeness  to 
any  particular  species  of  the  group,  the  general  likeness  mean- 
while being  profitable. 

The  second  condition  named  by  Wallace  is  correct  for 
Batesian  but  not  for  Miillerian  mimicry. 

The  fulfilment  of  the  third  condition  is  requisite  for  the 
success  of  Batesian  mimicry.  Bates  noted  that  none  of  the 
pierid  mimics  were  so  abundant  as  their  heliconiid  models. 
If  they  were,  their  protection  would  be  less ;  and  should  the 
mimic  exceed  its  model  in  numbers,  the  former  would  be  more 
subject  to  attack  than  the  latter.  Sometimes,  indeed,  as 
Miiller  found,  the  mimic  actually  is  more  common  than  the 
model ;  in  which  event,  the  consequent  extra  destruction  of  the 
mimic  would — at  least  theoretically — reduce  its  numbers  back 
to  the  point  of  protection. 

In  ]^Iiillerian  mimicry,  however,  the  inevitable  variation  in 
abundance  of  two  or  more  converging  and  protected  species  is 
far  less  disastrous ;  though  when  two  species,  equally  distaste- 
ful, are  involved,  the  rarer  of  the  two  has  the  advantage,  as 
Fritz  Miiller  has  shown.  His  lucid  explanation  is  essentially 
as  follows : 

Suppose  that  the  birds  of  a  region  have  to  destroy   1,200 


2  28  ENTOMOLOGY 

butterflies  of  a  distasteful  species  before  it  becomes  recognized 
as  such,  and  that  there  exist  in  this  region  2,000  individuals 
of  species  A  and  10,000  of  species  B ;  then,  if  they  are  diif event 
in  appearance,  each  will  lose  1,200  individuals,  but  if  they  are 
deceptively  alike,  this  loss  will  be  divided  among  them  in  pro- 
portion to  their  numbers,  and  A  will  lose  200  and  B  1,000.  A 
accordingly  saves  1,000,  or  50  per  cent,  of  the  total  number 
of  individuals  of  the  species,  and  B  saves  only  200,  or  2  per 
cent.  Thus,  while  the  relative  numbers  of  the  two  species  are 
as  I  to  5,  the  relative  advantage  from  their  resemblance  is  as 
25  to  I. 

If  two  or  more  distasteful  species  are  equally  numerous, 
their  resemblance  to  one  another  brings  nearly  equal  advan- 
tages. In  cases  of  this  kind — and  many  are  known — it  is 
sometimes  impossible  to  distinguish  between  model  and  mimic, 
as  all  the  participants  seem  to  have  converged  toward  a  com- 
mon protective  appearance,  through  an  interchange  of  features 
— the  "  reciprocal  mimicry  "  of  Dr.  Dixey. 

From  this  explanation,  the  superior  value  of  Miillerian  as 
compared  with  Batesian  mimicry  is  evident. 

The  fourth  condition — that  the  imitators  differ  from  the 
bulk  of  their  allies — holds  true  to  such  a  degree  that  even  the 
two  sexes  of  the  same  species  may  differ  extremely  in  colora- 
tion, owing  to  the  fact  that  the  female  has  assumed  the  like- 
ness of  some  other  and  protected  species.  The  female  of 
Papilio  merope,  indeed,  occurs  (as  was  just  mentioned)  under 
three  varieties,  which  mimic  respectively  three  entirely  dissim- 
ilar species  of  Danainre,  and  none  of  the  females  are  any- 
thing like  their  male  in  coloration  (Frontispiece,  Figs.  5-1 1). 
The  specific  identity  of  these  four  South  African  varieties  of 
merope  has  been  established  by  Trimen,  Marshall  and  other 
investigators. 

The  generally  accepted  explanation  for  these  remarkable 
but  numerous  cases  in  which  the  female  alone  is  mimetic,  is 
that  the  female,  burdened  with  eggs  and  consequently  sluggish 
in  flight  and  much  exposed  to  attack,  is  benefited  by  imitating 


ADAPTIVE    COLORATION  229 

a  species  which  is  ininnine;  while  the  male  has  had  no  such 
incentive — so  to  speak — to  become  mimetic.  Of  course,  there 
has  been  no  conscious  evolution  of  mimicry. 

Wallace's  iifth  stipulation  is  important,  but  should  read  this 
way:  ''The  imitation,  however  minute,  is  but  external  and 
visible  itsiiaHy,  and  never  extends  to  internal  characters  zvliich 
do  not  affect  the  external  appearance."  J^'or,  as  Poulton 
points  out,  the  alertness  of  a  beetle  which  mimics  a  wasp, 
implies  appropriate  changes  in  the  nervous  and  muscular  sys- 
tems. In  its  intent,  however,  Wallace's  rule  holds  good,  and 
by  disregarding  it  some  w-riters  strain  the  theory  of  mimicry 
beyond  reasonable  limits.  Some  have  said,  for  example,  that 
the  resemblance  between  caddis  flies  and  moths  is  mimicry; 
when  the  fact  is  that  this  resemblance  is  not  merely  superficial 
but  is  deep-seated;  the  entire  organization  of  Trichoptera 
shows  that  they  are  closely  related  to  Lepidoptera.  This  like- 
ness expresses,  then,  not  mimicry,  but  ai^nity  and  parallel 
development.  The  same  objection  applies  to  the  assumed 
cases  of  mimicry  within  the  limits  of  a  single  family,  as  be- 
tween two  genera  of  Heliconiidse  or  between  the  chrysomelid 
genera  Leuia  and  Diahrotica.     The  nearer  two   species  are 

related  to  each  other,  the  more  probable 

1  1  1    •       ■     -1     •       ■      1  Fig.  245. 

it  becomes  that  then"  smiilarity  is  due — 

not    to    mimicry — but    to    their   common 

ancestry. 

On   the   other   hand,    the   resemblance 

frequently  occurs  between  species  of  such 

-,•  ^c  ,       ■        ,  .  ,  .,  A       locustid,       Alvnnc- 

diiterent  orders  that  it  cannot  be  attrib-  cophana  faiiax,  which 
uted  to  affinity.     Illustrations  of  this  are     ^"^"^"es  an  ant.    Twice 

-^  natural        length.       From 

the    mimicry    of    the    honey    bee   by   the      brunner      von      wat- 

^  n  ^       1  1  •  •  TENWYL. 

drone  fly,  and  the  many  other  instances  m 
which  stinging  Hymenoptera  are  counterfeited  by  harmless 
flies  or  beetles.  A  locustid  of  the  Soudan  resembles  an  ant 
(Fig.  245),  and  the  resemblance,  by  the  w-ay,  is  obtained  in  a 
most  remarkable  manner.  Upon  the  stout  body  of  this  or-r 
thopteron  the  abdomen  of  an  ant  is  delineated  in  black,  the  rest 


230  ENTOMOLOGY 

of  the  body  being  light  in  color  and  inconspicuous  by  contrast 
with  the  black.  Indeed  the  various  means  by  which  a  super- 
ficial resemblance  is  brought  about  between  remotely  related 
insects  are  often  extraordinary. 

Irrespective  of  affinity,  insects  of  diverse  orders  may  con- 
verge in  wholesale  numbers  toward  a  central  protected  form. 
The  most  complete  examples  of  this  have  recently  been  brought 
to  light  by  ]\Iarshall  and  Poulton,  in  their  splendid  work  on 
the  bionomics  of  South  African  insects,  in  which  is  given,  for 
instance,  a  colored  plate  showing  how  closely  six  distasteful 
and  dominant  beetles  of  the  genus  Lyciis  are  imitated  by  nearly 
forty  species  of  other  genera — a  remarkable  example  of  con- 
vergence involving  no  less  than  eighteen  families  and  five  or- 
ders, namely,  Coleoptera,  Hymenoptera,  Hemiptera,  Lepidop- 
tera  and  Diptera.  Excepting  a  few  unprotected,  or  Batesian, 
mimics  (a  fly  and  two  or  three  beetles.),  this  association  is 
one  between  species  that  are  already  protected,  by  stings,  bad 
tastes  or  other  peculiarities.  In  other  words,  here  is  Miiller- 
ian  mimicry  on  an  immense  scale ;  and  if  Miillerian  mimicry 
is  profitable  when  only  two  species  are  concerned,  what  an 
enormous  benefit  it  must  be  to  each  of  forty  participants ! 

Strength  of  the  Theory. — Evidently  the  theory  of  mimicry 
rests  upon  the  assumption  that  the  mimics,  by  virtue  of  their 
mimicry,  are  specially  protected  from  insectivorous  foes.  Un- 
til the  last  few  years,  however,  there  was  altogether  too  little 
positive  evidence  bearing  upon  the  assumption  itself,  though 
this  was  supported  by  such  scattered  observations  as  were 
available.  The  oft-repeated  assertion  that  this  lack  of  evi- 
dence was  due  simply  to  inattention  to  the  subject,  has  been 
proved  to  be  true  by  the  decisive  results  recently  gained  in  the 
tropics  by  several  competent  investigators  who  have  been  able 
to  give  the  subject  the  requisite  amount  of  attention. 

From  his  observations  and  experiments  in  India,  Frank 
Finn  concludes : 

"  I.  That  there  is  a  general  appetite  for  butterflies  among 
insectivorous  birds,  even  though  they  are  rarely  seen  when 
wild  to  attack  them. 


ADAPTIVE    COLORATION  23  I 

''  2.  That  many,  probably  most  species,  dislike,  if  not  in- 
tensely, at  any  rate  in  comparison  with  other  butterflies,  the 
warningly-colored  Danainae,  Acrcca  violcc,  Delias  eucharis,  and 
Papilio  aristolocliicc;  of  these  the  last  being-  the  most  distaste- 
ful, and  the  Danainae  the  least  so. 

"  3.  That  the  mimics  of  these  are  at  any  rate  relatively 
palatable,  and  that  the  mimicry  is  commonly  effectual  under 
natural  conditions. 

"  4.  That  each  bird  has  separately  to  acquire  its  experience, 
and  well  remembers  what  it  has  learned. 

"  That  therefore  on  the  whole,  the  theory  of  Wallace  and 
Bates  is  supported  by  the  facts  detailed  in  this  and  my  former 
papers,  so  far  as  they  deal  with  birds  (and  with  the  one  mam- 
mal used).  Professor  Poulton's  suggestion  that  animals  may 
be  forced  by  hunger  to  eat  unpalatable  forms  is  also  more 
than  confirmed,  as  the  unpalatable  forms  were  commonly  eaten 
without  the  stimulus  of  actual  hunger — generally,  also,  I  may 
add,  without  signs  of  dislike." 

Though  insects  have  many  vertebrate  and  arthropod  ene- 
mies, it  is  probable  that  the  evolution  of  mimetic  resemblance, 
implying  warning  coloration,  has  been  brought  about  chiefly 
by  insectivorous  birds. 

Neglecting  papers  of  minor  importance,  we  may  pass  at 
once  to  the  most  important  contribution  upon  this  subject — 
the  voluminous  w^ork  of  Marshall  and  Poulton  upon  mimicry 
and  warning  colors  in  South  African  insects.  These  investi- 
gators have  found  that  birds  are  to  be  counted  as  the  principal 
enemies  of  butterflies;  that  the  Danainae  and  Acrseinse,  which 
are  noted  as  models,  are  particularly  immune  from  destruc- 
tion, while  unprotected  forms  suffer;  and  that  mimicking, 
though  palatable  species,  share  the  freedom  of  their  models. 
The  same  is  true  of  beetles,  of  which  Coccinellidae,  Mala- 
codermidre  (notably  Lyciis) ,  Cantharidse  and  many  Chryso- 
melidcC  serve  as  models  for  many  other  Coleoptera,  being 
"  conspicuous  and  constantly  refused  by  insect-eaters."  In 
short,  the  splendid  work  of  Marshall  and  Poulton  tends  to 


232  ENTOMOLOGY 

place  the  theory  of  Batesian  and  Miillerian  mimicry  upon  a 
substantial  foundation  of  observational  and  experimental 
evidence. 

In  regard  to  the  important  cjuestion — do  birds  avoid  un- 
palatable insects  instinctively  or  only  as  the  result  of  experi- 
ence— the  evidence  is  all  one  way.  Several  investigators,  in- 
cluding Lloyd  Morgan,  have  found  that  newly-hatched  birds 
have  no  instinctive  aversions  as  regards  food,  but  test  every- 
thing, and  (except  for  some  little  parental  guidance)  are 
obliged  to  learn  for  themselves  what  is  good  to  eat  and  what 
is  not.  This  experimental  evidence  that  the  discrimination  of 
food  by  birds  is  due  solely  to  experience,  was  evidently  highly 
necessary  to  place  the  theory  of  mimicry — especially  the  Miil- 
lerian theory — upon  a  sound  basis. 

Though  butterflies  as  a  group  are  much  subject  to  the  at- 
tacks of  birds  in  the  tropics,  there  are  very  few  recorded  in- 
stances of  this  for  our  temperate  region.  It  may  then  be 
asked,  what  advantage  does  the  "  viceroy  "  (Fig.  243,  B)  gain 
by  resembling  the  "  monarch,"  in  a  region  where  all  butter- 
flies are  exempt  from  destruction  by  birds?  In  reply,  it  may 
be  said  that  the  premise  of  the  argument  is  as  yet  little  more 
than  an  assumption,  because  so  little  attention  has  been  given 
to  the  relations  between  birds  and  butterflies  in  our  own  coun- 
try. Or,  admitting  the  premise,  it  may  be  said  that  the  resem- 
blance was  advantageous  once,  if  not  now ;  and  that  in  any 
event,  the  departure  of  archippus  from  its  congeners  toward 
one  of  the  Danainic — a  famous  group  of  "  models  "  in  the 
tropics — is  unintelligible  except  as  an  instance  of  mimicry. 

Granting  that  mimicry  is  upon  the  whole  advantageous,  it 
becomes  important  to  learn  just  how  far  the  advantage  ex- 
tends ;  and  we  find  that  mimicry  is  not  of  universal  effective- 
ness. Even  the  highly  protected  Heliconiina;  and  Danaina^ 
are  food  for  some  predaceous  insects.  In  this  country,  as 
Judd  has  observed,  the  drone-fly  (Erisfalis  fciia.v),  which 
mimics  the  honey  bee,  is  eaten  by  the  kingbird  and  the  phoebe; 
the  kingbird,  indeed,  eats  the  honey  bee  itself,  but  is  said  to 


ADAPTIVE    COLORATION  233 

pick  out  the  drones;  chickens  also  (hscriminate  l)et\\een  ch'ones 
and  workers,  eating  the  former  and  avoicHng  the  latter.  Bum- 
ble bees  and  wasps,  imitated  by  many  other  insects,  are  them- 
selves eaten  by  the  .kinoi)ird,  catbird  and  several  other  birds, 
thoug-h  it  is  not  known  whether  the  stingless  males  of  these 
are  singled  out  or  not.  Such  facts  as  these  do  not  discredit 
the  general  theory  of  mimicry  but  point  out  its  limits. 

Evolution  of  Mimicry. — Natural  selection  gives  an  adequate 
explanation  of  the  e\-olution  of  a  mimetic  pattern.  Before 
accepting  this  explanation,  however,  we  must  inquire:  (i) 
What  were  the  tirst  stages  in  the  development  of  a  mimetic 
pattern?  (2)  What  evidence  is  there  that  every  step  in  this 
development  was  vitally  useful,  as  the  theory  demands  that  it 
should  be  ?  These  pertinent  questions  have  been  answered  by 
Darwin.  Wallace,  Miiller,  Dixey  and  several  other  authorities. 

The  incipient  mimic  must  have  possessed,  to  begin  with,  col- 
ors or  patterns  that  were  capable  of  mimetic  development; 
evidently  the  raw  material  must  have  been  present.  Now 
IMiiller  and  Dixey  in  particular  have  called  attention  to  the 
fact  that  many  pierids  have  at  least  touches  of  the  reds,  yellows 
and  other  colors  that  are  so  conspicuous  in  the  heliconids. 
More  than  this,  however,  Dixey  has  demonstrated — as  appears 
clearly  from  his  colored  figures — a  complete  and  gradual  tran- 
sition from  a  typical  non-mimetic  pierid,  Pieris  locusta,  to  the 
mimetic  pierid  Mylothris  pyrrha,  the  female  of  which  imitates 
Heliconius  numata.  He  traces  the  transition  chiefly  through 
the  males  of  several  pierid  species — for  the  males,  though  for 
the  most  part  white  (the  typical  pierid  color),  "  show  on  the 
under  surface,  though  in  varying  degrees,  an  approach  towards 
the  Heliconiine  pattern  that  is  so  completely  imitated  by  their 
mates.  These  partially  developed  features  on  the  under  sur- 
face of  the  males  [compare  Figs.  2  and  3  of  Frontispiece]  en- 
able us  to  trace  the  history  of  the  growth  of  the  mimetic  pat- 
tern." Starting  from  Pieris  lociisia,  it  is  an  easy  step  to 
Mylothris  lypera,  thence  to  M.  lorcna,  and  from  this  to  the 
mimetic  M.  pyrrha.     '"  Granted  a  beginning,  howe\'er  small, 


2  34  ENTOMOLOGY 

such  as  the  basal  red  touches  in  the  normal  Pierines,  an  elabo- 
rate and  practically  perfect  mimetic  pattern  may  be  evolved 
therefrom  by  simple  and  easy  stages." 

Furthermore  (in  answer  to  the  second  cjuestion),  it  does  not 
tax  the  imagination  to  admit  that  any  one  of  these  color  pat- 
terns has — at  least  occasionally — been  sufficiently  suggestive 
of  the  heliconid  type  to  preserve  the  life  of  its  possessor;  espe- 
cially when  both  bird  and  insect  were  on  the  wing  and  perhaps 
some  distance  apart,  when  even  a  momentary  flash  of  red  or 
yellow  from  a  pierid  might  be  enough  to  save  it  from  attack. 

It  is  highly  desirable,  of  course,  that  this  plausible  explana- 
tion should  be  tested  as  far  as  possible  by  observations  in  the 
field  and  by  experiments  as  well. 

Adaptive  Colors  in  General. — Several  classes  of  adaptive 
colors  have  been  discriminated  and  defined  by  Poulton,  whose 
classification,  necessarily  somewhat  arbitrary  but  nevertheless 
very  useful,  is  given  below,  in  its  abridged  form. 

I.  APATETIC  COLORS. — Colors  resembling  some  part  of  the  en- 
vironment or  the  appearance  of  another  species. 

A.  Cryptic  Colors. — Protective  and  Aggressive  Resemblances. 

1.  Procryptic     colors. — Protective     Resemblances. — Conceal- 

ment as  a  protection  against  enemies.     Example :  Kal- 
lima  butterfly. 

2.  Anticryptic    colors. — Aggressive    Resemblances. — Conceal- 

ment in  order  to  facilitate  attack.     Example  :   Mantids 
with    leaf-like   appendages. 

B.  PsEUDOSEMATic  CoLORS. — False  warning  and  signalling  colors. 

1.  Pscudaposcmatic  colors. — Protective  ^Mimicry.     Example: 

Bee-like  fly. 

2.  Pscudcpiscmatic  colors. — Aggressive  Mimicry  and  Allur- 

ing Coloration.     Examples :   Volucclla,  resembling  bees 
(Fig.   246)  ;    F'lower-like  mantid. 
II.  SEMATIC  COLORS.— Warning  and  Signalling  Colors. 

1.  Aposematic  colors. — Warning  Colors.     Examples:  Gaudy 

colors    of    stinging   insects. 

2.  Episcmatic  co/or.?.— Recognition  IMarkings. 

III.  EPIGA^IIC  COLORS.— Colors  Displayed  in  Courtship. 

Such  of  these  classes  as  have  not  already  been  discussed 
need  brief  reference. 


ADAPTIVE    COLORATION 

Fig.  246. 


235 


Aggressive    mimicry.     On   the    left,    a    bee,    Rombiis    iiiastniciUns;   on    tlic    right,    a    fly, 
Volucclla    hombylans.     Natural    size. 

Aggressive  Resemblances. — The  reseml:)lancc  of  a  car- 
ni\orons  animal  to  its  surroundings  may  not  only  be  protec- 
tive l)ut  may  also  enable  it  to  approach  its  prey  undetected,  as 
in  the  case  of  the  polar  bear  or  the  tiger.  Among  insects, 
however,  the  occurrence  of  aggressive  resemblance  is  rather 
doubtful,  even  in  the  case  of  the  leaf-like  mantids. 

Aggressive  Mimicry. — Under  this  head  are  placed  those 
cases  in  which  one  species  mimics  another  to  which  it  is  hostile. 
The  best  known  instance  is  furnished  by  European  flies  of  the 
genus  Volucclla,  whose  larv?e  feed  upon  those  of  bumble  bees 
and  wasps.  The  flies  bear  a  close  resemblance  to  the  bees, 
owing  to  which  it  is  supposed  that  the  former  are  able  to  enter 
the  nests  of  the  latter  and  lay  their  eggs. 

Alluring  Coloration. — The  best  example  of  this  phenom- 
enon is  afforded  by  an  Indian  mantid,  Gongylus  gongyloidcs, 
which  resembles  so  perfectly  the  brightly  colored  flowers 
among  which  it  hides  that  insects  actually  fly  straight  into  its 
clutches. 

Recognition  Markings. — Though  these  are  apparently  im- 
portant among  mammals  and  birds,  as  enabling  individuals  of 
the  same  species  quickly  to  recognize  and  follow  one  another, 
no  special  markings  for  this  purpose  are  known  to  occur  among 
insects,  not  excepting  the  gregarious  migrant  species,  such  as 
Anosia  plcxippns  and  the  Rocky  Mountain  locust. 

Epigamic  Colors. — Among  birds,  frequently,  the  Ijright  col- 
ors of  the  male  are  displayed  during  courtship,  and  their  evo- 


230  ENTOMOLOGY 

lution  has  been  attributed  by  Darwin  and  many  of  his  follow- 
ers to  sexual  selection— a  highly  debatable  subject.  Among 
insects,  however,  no  such  phenomenon  has  been  found ;  when- 
ever the  two  sexes  differ  in  coloration  the  difference  does  not 
appear  to  facilitate  the  recognition  of  even  one  sex  by  the 
other. 

Evolution  of  Adaptive  Coloration. — Natural  selection  is 
the  only  theory  of  any  consequence  that  explains  the  highly 
involved  phenomena  of  adaptive  coloration.  Against  such 
vague  and  unsupported  theories  as  the  action  of  food,  climate, 
laws  of  growth  or  sexual  selection,  natural  selection  alone 
accounts  for  the  multitudinous  and  intricate  correlations  of 
color,  pattern,  form,  attitude,  movement,  place,  time,  etc.,  that 
are  necessary  to  the  development  of  a  perfect  case  of  protective 
resemblance  or  mimicry.  Natural  selection  cannot,  of  course, 
originate  colors  or  any  other  characters,  its  action  being  re- 
stricted to  the  preservation  and  accumulation  of  such  advan- 
tageous variations  as  may  arise,  from  whatever  causes.  As 
Poulton  says,  the  vast  body  of  facts,  utterly  meaningless  under 
any  other  theory,  become  at  once  intelligible  as  they  fall  har- 
moniously into  place  under  the  principle  of  natural  selection, 
to  which,  indeed,  they  yield  the  finest  kind  of  support. 


CHAPTER    VII 

ORIGIN    OF   ADAPTATIONS    AND    OF    SPECIES 

T.  .Adaptations 

Organic  Evolution. — Oro-anic  evolution  is  essentially  the 
evolution  of  adaptive  structures  and  functions.  There  remain 
to  be  explained,  however,  non-adaptive  structures  and  func- 
tions, and  no  theory  of  evolution  is  adequate  which  does  not 
account  for  the  useless  as  well  as  the  useful  characters. 

Existing  structures  are  due  to  the  nature  of  the  organism 
and  the  nature  of  the  environment ;  in  other  words,  are  results 
of  the  activity  of  protoplasm  under  the  influence  of  environ- 
mental forces.  Variations  arise  which  are  useful  or  not  and 
either  transmissible  or  not.  Useful  transmissible  variations 
not  only  remain  but  tend  to  become  more  nearly  perfect ;  while 
useless  variations  tend  to  disappear. 

The  various  theories  of  organic  evolution  difi^er  chiefly  in 
their  answers  to  these  questions:  (i)  What  is  the  nature  of 
variations  and  how  do  they  arise?  Variations  are  classed  as 
either  continuous  or  discontinuous ;  adaptive  or  unadaptive. 
In  asexual  organisms,  variations  are  brought  about  by  the 
direct  influence  of  temperature,  light  and  other  primary  fac- 
tors upon  protoplasm ;  in  sexual  organisms,  variations  are  due 
to  another  cause  as  well,  namely,  the  union  of  two  kinds  of 
protoplasm.  In  any  given  case  of  variation,  how  much  is  due 
immediately  to  protoplasm  and  how  much  to  the  environment  ? 
(2)  What  kinds  of  variations  are  transmissible?  Discontinu- 
ous variations  (sports)  are  strongly  transmissible  as  a  rule, 
while  continuous  (individual)  variations  are  often  non-trans- 
missible; though  it  is  often  dii^cult  to  decide  whether  they  are 
transmissible  or  not.  Each  kind  of  variation  has  to  be  exam- 
ined separately,  on  its  own  merits.     Difficulties  arise  from  the 

237 


238  ENTOMOLOGY 

fact  that  some  variations  which  appear  in  successive  genera- 
tions are  due  not  to  inheritance  but  to  the  direct  action  of  the 
environment  on  each  successive  generation ;  also  to  the  fact 
that  some  structural  changes  may  have  been  brought  about  by 
selection  of  some  sort,  rather  than  by  inheritance.  Are  the 
results  of  use  or  disuse  or  mutilation  inheritable?  It  has  not 
been  proved  as  yet  that  these  "  acquired  characters  "  are 
transmissible.  On  the  other  hand,  experiments  show  that 
some  organisms  can  become  acclimatized  to  unusual  degrees 
of  heat,  density,  etc.,  through  inheritance,  in  cases  where  selec- 
tion does  not  enter  into  the  problem.  JMuch  of  the  confusion 
attending  the  discussion  of  "  the  inheritance  of  acquired  char- 
acters "  has  been  due  to  disagreements  as  to  what  is  meant  by 
the  term  "acquired  characters."  (3)  What  are  the  secondary 
influences  that  have  brought  about  the  evolution  of  structures  ? 
Of  these  influences,  natural  selection  and  isolation  are  by  far 
the  most  important;  while  in  some  instances  extensive  struc- 
tural adaptations  have  arisen  spontaneously,  without  a  long 
-course  of  evolution. 

Natural  Selection. — The  more  intricate  adaptations  of 
organism  to  environment,  however,  are  for  the  most  part  inex- 
plicable without  the  aid  of  Darwin's  and  Wallace's  theory  of 
natural  selection.  After  almost  fifty  years  of  searching  criti- 
cism and  even  violent  opposition,  this  theory,  though  modified 
in  some  respects,  remains  essentially  as  it  was  formulated,  and 
is  at  present  the  working  hypothesis  of  most  naturalists.  This 
doctrine  is  here  outlined  in  its  several  factors. 

Excessive  Multiplication. — Any  one  species  of  animal  or 
plant,  were  its  multiplication  unchecked,  would  soon  cover  the 
earth.  The  progeny  of  a  single  aphid  in  ten  generations,  as 
•calculated  by  Huxley,  would  "  contain  more  ponderable  su1v 
stance  than  five  hundred  millions  of  stout  men ;  that  is,  more 
than  the  whole  population  of  China."  The  hop  aphid  (Phor- 
odon  hiimuli),  studied  by  Riley,  has  thirteen  generations  a 
year,  consisting  entirely  of  females  up  to  the  last  generation. 
Assuming  that  each  female  produces  100  young  and  that  the 


ORIGIN    OF    ADAPTATIONS    AND    OF    SPECIES  239 

increase  is  unchecked,  the  number  of  individuals  of  the  twelfth 
generation,  as  the  descendants  of  a  single  female  of  the  first 
generation,  would  be  ten  sextillions.  These  if  placed  in  a 
single  file,  allowing  lo  aphids  to  an  inch,  would  form  a  line  so 
long  that  light  itself,  traveling  at  the  rate  of  186,000  miles 
per  second,  would  require  over  2,690  years  to  go  from  one 
end  of  the  line  to  the  other. 

As  it  is,  many  species  become  temporarily  dominant  under 
favorable  conditions;  for  example,  the  Rocky  Mountain  locust, 
chinch  bug  and  gypsy  moth.  Even  one  of  the  least  prolific 
species  would  predominate  in  a  surprisingly  short  time,  were 
it  permitted  to  increase  in  its  normal  geometrical  ratio.  The 
rate  of  sexual  reproduction  is  highest  in  fishes  and  insects.  An 
insect  averages  one  or  two  hundred  eggs,  while  some  forms, 
as  queen  termites,  lay  them  by  thousands. 

Struggle  for  Existence. — Although  a  single  species  is 
potentially  capable  of  covering  the  earth,  there  actually  are  at 
least  1,000,000  species  of  insects,  not  to  mention  250,000  spe- 
cies of  other  animals  and  some  500,000  kinds  of  plants.  This 
means  a  tremendous  prevention  of  reproduction  among  the 
individuals  of  any  one  species — an  intense  "  struggle  for  ex- 
istence," as  Darwin  termed  it.  Among  plants  and  the  lower 
animals,  comparatively  few  individuals  survive  and  reproduce ; 
the  majority  die.  The  agents  of  destruction  are  manifold, 
each  species  having  its  own  army  of  enemies,  organic  and  in- 
organic. Thus  insects  are  subject  to  unfavorable  conditions 
of  temperature  and  moisture,  to  bacterial  and  fungous  dis- 
eases, vertebrate  and  invertebrate  enemies,  accidents,  etc. 
The  aphids  are  at  the  same  time  among  the  most  prolific  and 
the  most  defenceless  of  animals.  These  delicate  insects  suc- 
cumb to  very  slight  mechanical  shocks  and  are  killed  by  ex- 
tremes of  temperature  that  most  other  insects  can  endure. 
They  are  often  washed  off  their  food  plants  by  rain.  Their 
rate  of  reproduction  decreases  if  their  food  plant  receives  in- 
sufficient moisture.  Aphids  form  the  chief  food  of  coccinellid 
larvae  and  beetles,  are  preyed  upon  by  chrysopid  and  syrphid 


240  ENTOMOLOGY 

larvje,  parasitized  by  Braconidse  and  Chalcididse,  carried  off 
by  some  of  the  digger-wasps  (Mimesidae,  Pemphredonidje), 
and  devoured  by  ants,  carabids,  other  insects,  spiders,  and  some 
birds,  as  the  chickadee.  In  damp  weather,  aphids  are  killed 
in  countless  numbers  by  a  fungous  disease.  In  short,  the 
aphid  is  threatened  in  every  direction. 

Elimination  of  the  Unfit. — In  the  intense  "  struggle  for 
existence,"  as  it  is  commonly,  though  misleadingly,  called, 
those  comparatively  few  individuals  that  survive  do  so  mani- 
festly by  virtue  of  certain  advantages  over  their  less  fortunate 
fellows.  One  egg  can  stand  a  little  more  cold  than  another; 
one  beetle  drops  to  the  ground  when  disturbed  and  thus 
escapes  an  attacking'  bird,  while  its  companions  remain  in  place 
and  are  destroyed ;  some  individuals  escape  by  surpassing  their 
fellows  in  locomotor  ability  or  by  resembling  the  surface  on 
which  they  happen  to  rest. 

Such  fortunate  individuals  live  to  transmit  their  advantage- 
ous peculiarities  to  their  progeny,  while  the  less  favored  indi- 
viduals succumb.  The  progeny  inherit  the  life-saving  pecu- 
liarities in  differing  degrees,  and  the  least  favored  of  the 
progeny  are  again  weeded  out.  Thus  by  the  continual  elim- 
ination of  individuals  that  vary  in  unfavorable  directions,  the 
individuals  that  remain  become  better  and  better  adapted  to 
the  surrounding  conditions  of  life,  through  the  preservation 
and  accumulation  of  advantageous  variations.  This  preser- 
vation and  accumulation  of  advantageous  variations  through 
.the  destruction  of  disadvantageous  ones  is  the  essence  of  nat- 
ural selection,  or  the  "  survival  of  the  fittest." 

Favorable  variations  may  have  been  so  slight  and  infre- 
quent as  to  have  required  geological  ages  for  their  accumula- 
tion. On  the  other  hand,  adaptive  variations  are  sometimes 
so  extensive  from  the  beginning  as  to  lead  some  writers  to 
doubt  that  these  variations  are  preserved  and  improved  by 
natural  selection. 

Variation. — Natural  selection  cannot  originate  useful  char- 
acters, of  course,  but  is  limited  to  the  preservation  and  accu- 


ORIGIN    OF    ADAPTATIONS    AND    OF    SPECIES  24 1 

mulation  of  such  advantageous  variations  as  already  exist. 
Variation,  then,  is  the  basis  of  natural  selection.  Though  the 
question  of  the  origin  of  variations  is  still  unsettled,  the  fact 
of  their  occurrence  in  a  manner  sufficient  for  the  purposes  of 
natural  selection  is  beyond  dispute.  No  two  individuals  of  a 
species  are  ever  exactly  alike  in  structure  or  jjehavior,  and 
their  differences  furnish  the  material  for  the  operation  of 
natural  selection. 

Two  classes  of  variations  are  distinguished  on  the  basis  of 
the  amount  of  variation:  (i)  coiitiiinous  {individual)  varia- 
tions, of  small  extent,  intergrading  with  one  another  and  with 
the  typical  form;  and  (2)  discoufiiuious  variations  (sports), 
or  considerable  and  isolated  departures  from  the  normal  con- 
dition. Furthermore,  variations  of  either  class  are  adaptive 
or  unadaptive,  the  latter  kind  being  either  harmful  or  simply 
neutral. 

Origin  of  Adaptive  Variations. — Xatural  selection,  as 
was  said,  does  not  begin  to  operate  until  useful  variations  are 
already  in  existence ;  and  the  origin  of  these  primary  adaptive 
variations  is  a  question  quije  distinct  from  that  of  their  sub- 
sequent preservation  and  accumulation  by  natural  selection. 

That  all  adaptive  variations  are  due  to  the  response  of  pro- 
toplasm to  environmental  influences  (using  the  term  "  envi- 
ronment "  in  its  widest  sense),  it  goes  without  saying.  These 
variations  are,  however,  either  direct  or  indirect.  Direct 
variations,  appearing  first  in  the  soma,  or  body,  of  the  organ- 
ism, are  termed  somatogenic;  indirect  variations,  apparently 
spontaneous,  and  due  immediately  to  the  germ  cells,  are  termed 
blastogenic.  Weismann  places  somatogenic  variations,  ac- 
cording to  their  origin,  into  three  categories:  (i)  injuries, 
(2)  functional  z'ariatious,  and  (3)  variations  depending  on 
the  so-called  "  influences  of  environment,"  these  influences 
being  mainly  clinuitic.  These  three  kinds  will  receive  brief 
consideration. 

Injuries. — There  appears  to  be  no  good  evidence  that  in- 
juries or  mutilations  can  be  transmitted.  Nearly  all  the  ex- 
•7 


242  ENTOMOLOGY 

periments  upon  the  subject  have  given  decidedly  negative 
results.  Thus  Weismann  found  that  the  amputation  of  the 
tails  of  hundreds  of  mice,  down  to  the  nineteenth  generation, 
had  no  influence  on  the  tails  of  the  descendants. 

Mechanical  injuries  to  the  body  of  an  organism  are  merely 
casual,  or  accidental,  effects  of  the  environment  and  appear  to 
have  no  influence  upon  the  germ  cells.  From  the  standpoint 
of  adaptation,  injuries  are  only  of  minor  importance. 

Functional  Variations. — While  it  is  certain  that  the  use 
or  disuse  of  organs  affects  their  form  in  the  individual,  it 
remains  doubtful  whether  the  effects  of  use  and  disuse  are 
transmissible.  Weismann  and  his  followers  contend  that  they 
are  not.  On  the  other  hand,  Neo-Lamarckians,  as  Cope, 
Hyatt,  H.  F.  Osborn,  Packard  and  Eimer,  have  maintained 
that  they  are.  Weismann  admits,  however,  that  both  use  and 
disuse  may  lead  indirectly  to  variations,  "  the  former  when- 
ever an  increase  as  regards  the  character  concerned  is  useful, 
and  the  latter  in  all  cases  in  which  an  organ  is  no  longer  of 
any  importance  in  the  preservation  of  the  species  " ;  and  that 
these  variations  may  be  acted  upon  by  natural  selection. 
Thus,  in  a  few  words,  the  question  stands. 

Environmental  Variations. — Under  this  head  may  be 
classed  such  variations  as  are  due  directly  to  climate,  nutrition 
and  other  primary  environmental  influences.  It  is  certain 
that  changes  of  temperature,  light,  and  food,  for  example, 
cause  corresponding  changes  of  form  and  function  in  the  indi- 
vidual organism ;  though  the  inheritance  of  these  changes 
directly  induced  by  the  environment  is  the  subject  of  much 
debate. 

Dallinger  took  flagellate  infusorians  that  at  first  would  die 
at  a  temperature  of  23°  C,  and  by  slowly  raising  the  tempera- 
ture through  several  years,  brought  them  safely  to  a  tempera- 
ture of  70^  C.  There  was  some  mortality,  to  be  sure,  in  his 
experiments,  but  other  experimenters  have  obtained  similar 
results  without  the  loss  of  a  single  individual,  and  therefore — 
it  is  important  to  note — without  the  entrance  of  natural  selec- 


ORIGIN    OF    ADAPTATIONS    AND    OF    SPECIES  243 

tion.  This  prog-ressive  acclimatization  of  successive  genera- 
tions of  an  organism  to  heat  is  clearly  due  in  large  measure  to 
heredity.  So  also  in  the  case  of  the  entomostracan  Artemia, 
whose  specific  form  Schmankewitsch  succeeded  in  changing, 
by  increasing  the  salinity  of  the  water  in  which  the  animal 
lived.  Here,  again,  the  adaptation  was  brought  about  with- 
out the  aid  of  selection. 

Poulton's  already-mentioned  experiments  on  larvae  and 
pupcT  show  that  these  may  become  protectively  colored  as  the 
direct  effect  of  the  surrounding  light  on  the  organism.  Here, 
of  course,  the  possible  influence  of  natural  selection  can  scarcely 
be  excluded,  though  the  fact  remains  that  the  color  resem- 
blances are  initiated  directly  by  the  stimulus  of  light  upon 
protoplasm. 

Protoplasm  itself  is  to  a  certain  extent  adaptive,  in  that  it 
may  become  acclimatized  to  untoward  conditions  of  heat,  light 
and  other  stimuli.  From  this  point  of  view,  Henslow's  theory 
of  self-adaptation  in  plants  deserves  more  consideration  than 
it  has  received,  though  Henslow  did  not  adopt  the  theory  of 
natural  selection. 

Blastogenic  Variations. — According  to  Weismann,  only 
congenital  variations  are  inheritable,  i.  e.,  only  those  that  result 
from  modifications  of  the  germ  plasm.  He  holds  that  while 
all  variations  are  due  ultimately  to  external  influences,  the 
processes  of  reproduction  (conjugation  in  unicellular,  and 
sexual  reproduction  in  multicellular  organisms)  furnish  fresh 
combinations  of  individual  variations  for  the  operation  of  nat- 
ural selection,  and  that  this  is  the  chief  purpose  of  aniphimixis, 
or  "  the  mingling  of  two  individuals  or  of  their  germs." 

Inheritance  of  Acquired  Characters. — Weismann  and  his 
followers,  in  opposition  to  the  Neo-Lamarckians,  hold  that 
somatogenic,  or  acquired,  characters  are  not  transmissible ; 
that  every  permanent  (hereditary)  variation  proceeds  from 
the  germ. 

The  subject  of  the  inheritance  of  acquired  characters  has 
aroused  no  end  of  discussion,  much  of  which  has  been  fruit- 


244  ENTOMOLOGY 

less,  chiefly  for  two  reasons.  First,  there  is  no  httle  disagree- 
ment as  to  what  is  meant  by  the  term  "  acquired  characters." 
An  acquired  character  arises,  not  in  the  germ  cells,  but  in  the 
soma,  or  body,  and  for  the  theoretical  transmission  of  the 
character  the  soma  must  affect  the  germ  cells  subsequently ; 
though  some  maintain  that  a  given  external  influence  may 
affect  both  soma  and  germ  plasm  at  the  same  time.  The  defi- 
nition of  acquired  characters  excludes  (i)  sports;  (2)  changes 
due  to  the  renewed  action  of  the  environment  upon  successive 
generations  of  an  organism;  (3)  changes  which  may  have 
been  due  to  selection.  Second,  having  defined  the  term,  it  is 
often  difficult  if  not  impossible  to  say  whether  a  given  charac- 
ter is  acquired  or  not.  Thus  in  an  acclimatization  experiment, 
if  heat,  for  example,  affects  first  the  soma  and  the  latter  affects 
the  germ  cells  subsequently,  we  have  an  example  of  the  inheri- 
tance of  an  acquired  character.  If,  however,  the  heat  affects 
soma  and  germ  plasm  simultaneously,  the  result  is  or  is  not 
the  inheritance  of  an  acquired  character,  according  as  one  de- 
fines the  term.  Indeed,  Weismann  himself  has  found  the 
greatest  difficulty  in  trying  to  explain  the  inheritance  of  "  cli- 
matic" variations  in  terms  of  his  well-known  hypothesis.  In 
fact,  the  distinction  between  acquired  and  non-acquired  charac- 
ters is  to  no  little  extent  artificial  and  arbitrary ;  and  too  strong 
an  insistence  upon  the  distinction  bars  the  way  to  the  solution 
of  the  more  important  question — What  kinds  of  variations  are 
inheritable  and  what  are  not  ? 

To  summarize :  Of  somatogenic,  or  acquired,  characters, 
( I )  injuries  or  mutilations  are  unadaptive  and  probably  unin- 
heritable.  (2)  Functional  variations  are  adaptive,  but  the 
subject  of  their  transmissibility  is  involved  in  doubt.  As  yet 
there  is  no  adequate  experimental  evidence  upon  the  subject, 
the  discussion  of  which,  therefore,  is  based  chiefly  on  theoret- 
ical grounds.  There  is  a  strong  tendency,  however,  to  believe 
that  results  of  use  or  disuse  are  to  some  extent  transmissible 
to  the  benefit  of  succeeding  generations,  and  even  Weismann. 
the  chief  opponent  of  the  Neo-Lamarckians.  admits  that  the 


ORIGIN    OF    ADAPTATIONS    AND    OF    SPECIES  245 

effects  of  use  and  disuse  are  important  in  organic  evolution. 
(3)  Effects  of  climatal  inlluences  and  of  nutrition  arc  fre- 
quently adaptive  and  often  transmissible,  as  experiments  have 
proved.  There  is,  however,  much  difference  of  opinion  as  to 
the  precise  way  in  which  these  effects  are  transmitted. 

Incidental  Adaptations. — Many  leaf-eating  caterpillars 
and  grasshoppers  are  green  from  the  presence  of  chlorophyll 
in  their  l)odies;  they  owe  their  color  directly  to  their  food. 
Now  it  may  be  admitted  that  this  green  color  is  often  protec- 
tive, without  admitting  that  the  color  was  acquired  for  that 
purpose.  In  the  case  of  green  leaf-mining  caterpillars,  cer- 
tainly, the  color  appears  to  be  superfluous  for  protective  pur- 
poses. Even  variegated  protective  coloration  may  be  simply 
a  direct  effect  of  the  surrounding  kinds  of  light,  as  Poulton 
proved. 

Again,  take  the  various  tropisnis,  described  in  another 
chapter.  Often  they  are  adaptive  and  often  they  are  not ;  but 
they  occur  inevitably,  whether  they  result  advantageously  or 
not.  It  is  too  much  to  say  that  a  useful  structure  or  function 
appeared  because  of  its  usefulness.  It  first  appeared,  and  then 
proved  to  be  either  useful  or  not  useful.  If  useful,  a  structure 
may  save  the  life  of  its  possessor  and  possibly  be  transmitted  to 
the  next  generation ;  if  harmful,  it  is  self-eliminating. 

2.  Species 

Modifications  arise,  and  are  either  useful  or  not  to  their 
possessors.  For  the  systematist  who  aims  merely  to  distin- 
guish one  species  from  another,  this  distinction  matters  but 
little.  To  the  biologist,  however,  the  difference  is  an  essential 
one,  and  he  draws  a  line  between  specific  peculiarities  that  are 
adaptive  and  those  that  are  not  adaptive.  The  origin  of 
species  and  the  origin  of  adaptations  are  by  no  means  the 
same  thing. 

Darwin's  Origin  of  Species. — At  the  time  Darwin's  great 
W'Ork  was  written,  its  immediate  purpose  was  to  demonstrate 
a  process  of  organic  evolution;  and  this  object  was  accom- 


246  ENTOMOLOGY 

plished  in  the  most  forcible  way,  namely,  by  shattering  the 
traditional  belief  in  the  immutability  of  species.  Nowhere 
does  Darwin  imply  that  nature  is  striving  to  produce  "  spe- 
cies "  for  their  own  sake.  A  process  of  evolution  was  the 
theme  of  Darwin  and  its  key-note  was  adaptation. 

Indeed,  for  the  purposes  of  the  present  generation,  Dar- 
win's immortal  work  would  more  properly  be  entitled — The 
Evolution  of  Adaptations  by  Means  of  Natural  Selection. 
And  to  us,  who  now  ridicule  the  old  notion  of  the  special 
creation  of  species,  the  doctrine  of  natural  selection  appears  in 
a  fresh  light,  with  a  new  mission.  For,  in  the  words  of 
Romanes,  the  theory  is  "  primarily,  a  theory  of  adaptations, 
and  only  becomes  secondarily  a  theory  of  species  in  those  com- 
paratively insignificant  cases  where  the  adaptations  happen  to 
be  distinctive  of  the  lowest  order  of  taxonomic  division." 
The  opposite  view  he  compares  "  to  that  of  an  astronomer  who 
should  define  the  nebular  hypothesis  as  a  theory  of  the  origin 
of  Saturn's  rings.  It  is  indeed  a  theory  of  the  origin  of 
Saturn's  rings ;  but  only  because  it  is  a  theory  of  the  origin  of 
the  entire  solar  system,  of  which  Saturn's  rings  form  a  part. 
Similarly,  the  theory  of  natural  selection  is  a  theory  of  the 
entire  system  of  organic  nature  in  respect  of  adaptations, 
whether  these  happen  to  be  distinctive  of  particular  species 
only,  or  are  common  to  any  number  of  species."  It  should  be 
remembered,  of  course,  in  using  this  comparison,  that  not  all 
specific  characters  are  adaptive. 

As  regards  the  origin  of  species,  however,  there  are  several 
processes  at  work  besides  natural  selection.  Indeed,  Darwin 
himself  knew  this,  for  he  expressly  stated :  "  I  am  convinced 
that  natural  selection  has  been  the  most  important,  but  not  the 
exclusive,  means  of  modification." 

The  Conception  of  "Species." — What  is  a  "species"? 
The  only  practical  criterion  of  species  is  isolation,  or  separate- 
ness,  of  one  kind  or  another.  The  majority  of  our  "  species  " 
are  sharply  separated  from  one  another  by  structural  differ- 
ences ;   the  minority,   however,   blend   into  one  another,   and 


ORIGIN    OF    ADAPTATIONS    AND    OF    SPECIES  247 

have  so  many  characters  in  common  that  the  separation  into 
species  hecomes  an  arbitrary  matter,  depenchng  upon  the  g-ood 
judgment  of  the  systematist,  who  if  wise,  is  neither  a 
"'  Uimper  "  nor  a  "  sphtter."  At  present,  the  minutely  dis- 
criminating" powers  of  an  unfortunately  large  number  of  ento- 
mological systematists  are  displayed  in  an  extraordinary  mul- 
tiplication of  generic  and  specific  names,  often  to  the  sacrifice 
of  convenience  and  stability  of  nomenclature.  This  has  been 
carried  to  such  an  extent,  however,  that  a  reaction  has  already 
set  in;  and  there  is  now  some  promise  of  a  rational  termi- 
nology. 

Considering  characters  as  of  specific  importance  only,  it 
makes  no  immediate  difference  whether  they  are  adaptive  or 
not.  If  adaptive,  whatever  their  origin,  they  may  have  been 
developed  by  natural  selection;  if  not,  they  are  incidental,  and 
may  be  due  to  such  influences  as  those  next  to  be  referred  to. 

Climate  and  Food. — Naturalists  have  recorded  many  in- 
stances in  which  plants  or  animals  when  transferred  to  a  new 
climate  have  produced  ofTspring'  markedly  different  from  the 
parent  form.  The  term  climate,  however,  has  no  precise 
meaning  for  the  naturalist,  referring  as  it  does  collectively  to 
several  distinct  influences,  chief  among  which  are  tempera- 
ture, moisture,  light  and  (indirectly)  food  conditions.  Ex- 
perimental evidence  has  already  been  adduced  to  show^  that 
color  changes  in  insects  may  be  brought  about  as  direct  effects 
of  warmth,  cold,  light  or  food.  Some  of  these  color  varia- 
tions are  possibly  inheritable,  and  many  of  them,  artificially 
produced,  would  be  regarded  as  distinctive  of  new  species,  if 
found  in  a  state  of  nature.  In  fact,  the  distinction  between 
varieties  and  species  is  often  entirely  arbitrary ;  varieties  are 
incipient  species  and  it  is  often  impossible  to  draw  any  sharp 
line  between  the  two. 

Mutation  Theory. — De  Vries'  imitation  theory,  expounded 
in  1 90 1  as  the  result  of  nearly  twenty  years  of  experimenta- 
tion, is  at  present  an  absorbing  subject  of  study  and  discussion 
in  the  biological  world,  and  will  continue  to  be  for  many  years, 
until  the  full  bearing  of  the  theory  is  ascertained. 


248  ENTOMOLOGY 

De  Vries  has  produced  new  species  by  experimental  means 
and  without  the  aid  of  selection.  Moreover,  he  has  produced 
them  at  once,  showing  that  a  species  does  not  necessarily  re- 
quire hundreds  of  years  to  develop,  by  means  of  a  long-con- 
tinued process  of  selection. 

It  has  long  been  customary  to  draw  a  distinction  between 
individual  variations  and  sports.  Darwin  recognized  the  dis- 
tinction and  was  one  of  the  first  to  notice  the  extraordinary 
persistence  with  which  sports  are  transmitted,  as  compared 
with  the  relative  instability  of  individual  variations.  Not  a 
few  dominant  races  of  plants  and  animals  are  known  to  have 
arisen  from  sports,  and  the  belief  has  been  gaining  ground 
with  Bateson  and  others  that  species  also  have  to  some  extent 
arisen  from  sports,  rather  than  from  individual  variations; 
though  the  rarity  of  sports  as  compared  with  individual  varia- 
tions is  the  strongest  objection  to  this  theorv  as  a  theory  of 
the  origin  of  species  in  general. 

De  Vries,  however,  was  the  first  to  make  extensive  experi- 
ments on  sports,  or  imitations,  as  he  calls  them,  and  to  formu- 
late a  definite  theory  of  the  subject  from  a  considerable  body 
of  evidence.  He  regards  the  qualities  of  organisms  as  being 
built  up  of  definite  but  sharply  separated  units,  or  elements, 
which  combine  in  groups.  The  addition  of  a  new  unit  means 
a  mutation,  a  sudden  departure  from  the  normal  specific  form ; 
in  other  words,  a  new  species  may  arise  from  the  parent  form 
without  any  evident  gradation.  The  mutable  condition  exists 
only  at  times,  and  some  species  are  more  mutable  than  others. 
Acting  upon  this  as  a  hypothesis,  De  Vries  made  a  preliminary 
study  of  a  great  number  of  plants  in  order  to  find  one  in  its 
period  of  mutation,  and  at  length  selected  CEnothera  Lamarck- 
iana  (probably  a  variety  of  our  E.  biennis,  introduced  into 
Holland  from  America),  because  of  its  exceptionally  vigorous 
multiplication,  dispersion  and  variation.  By  careful  cultivation 
and  by  means  of  artificial  pollination,  he  succeeded  in  obtaining 
seven  or  more  new  species.  Most  of  these  remained  con- 
stant from  year  to  year  in  spite  of  intercrossing.     ]\Ioreover, 


ORIGIN    OF    ADAPTATIONS    AND    OF    SPECIES  249 

cross  pollination  was  not  necessary  to  the  prodnction  of  new 
species  by  mutation,  and  when  employed  did  not  accelerate  the 
results  materially.  As  a  botanist,  De  Vries  confined  his  inves- 
tigations to  plants,  but  his  g-eneral  conclusions  are  perhaps 
equally  applicable  to  animals,  and  his  experiments  are  doulit- 
less  being-  repeated  by  zoologists. 

Through  his  exhaustive  experiments,  De  Vries  has  partly 
attained  a  long-desired  object,  in  that  he  has  removed  the  ques- 
tion of  the  origin  of  some  species  "  from  the  purely  theoretical 
to  the  concrete." 

The  mutation  theory  is  not  primarily  a  theory  of  the  origin 
of  adaptive  characters.  It  endeavors  to  account  for  the  origin 
of  certain  characters,  which  may  or  may  not  prove  useful  to 
their  possessors.  Indeed,  one  great  merit  of  De  Vries'  theory 
is  that  it  affords  an  explanation  for  the  existence  of  variations 
which  are  not  useful.  Now  Darwdn  does  not  pretend  to 
account  for  the  origin  of  variations,  but  he  shows  how  given 
variations,  if  useful,  may  be  preserved  and  accumulated. 
Thus  the  theory  of  De  Vries  supplements  that  of  Darwin  and 
does  not  antagonize  it;  even  though  De  Vries  himself  takes 
much  pains  to  contrast  the  two  theories,  and  even  asserts  that 
new  species  arise  exclusively  as  mutations.  Both  theories, 
indeed,  are  theories  of  the  origin  of  species ;  but  according  to 
De  Vries,  specific  characters  spring  into  existence,  irrespective  of 
their  usefulness;  while  according  to  Darwin,  useful  characters, 
and  these  only,  are  premised,  as  the  starting  point  of  the  evolu- 
tion of  certain  kinds  of  species.  Thus,  as  another  has  said, 
natural  selection  begins  where  the  mutation  theory  leaves  off. 

Isolation. — The  theory  of  isolation  as  given  by  Gulick  and 
by  Romanes  is  highly  important  as  affording  an  explanation 
of  "  the  rise  and  continuance  of  specific  characters  which  need 
not  necessarily  be  adaptive  characters."  By  isolation  is  meant 
"  simply  the  prevention  of  intercrossing  between  a  separated 
section  of  a  species  or  kind  and  the  rest  of  that  species  or 
kind.  ...  So  long  as  there  is  free  intercrossing,  heredity 
cancels  variability,  and  makes  in  favor  of  fixity  of  type.     Only 


250  ENTOMOLOGY 

when  assisted  by  some  form  of  discriminate  isolation,  which 
determines  the  exchisive  breeding  of  hke  with  hke,  can  hered- 
ity make  in  favour  of  change  of  type,  or  lead  to  what  we  un- 
derstand by  organic  evolution."      (Romanes.) 

"  As  soon  as  a  portion  of  a  species  is  separated  from  the 
rest  of  that  species,  so  that  breeding  between  the  two  portions 
is  no  longer  possible,  the  general  average  of  characters  in  the 
separated  portion  not  being  in  all  respects  precisely  the  same 
as  it  is  in  the  other  portion,  the  result  of  in-breeding  among 
all  individuals  of  the  separated  portion  will  eventually  be  dif- 
ferent from  that  which  obtains  in  the  other  portion ;  so  that, 
after  a  number  of  generations,  the  separated  portion  may 
become  a  distinct  species  from  the  effect  of  isolation  alone. 
Even  without  the  aid  of  isolation,  any  original  difference  of 
average  characters  may  become,  as  it  were,  magnified  in  suc- 
cessive generations,  provided  that  the  divergence  is  not  harm- 
ful to  the  individuals  presenting  it,  and  that  it  occurs  in  a 
sufficient  proportional  number  of  individuals  not  to  be  imme- 
diately swamped  by  intercrossing."      (Romanes.) 

Of  the  many  modes  of  isolation,  the  most  important  are  the 
geographical  and  the  physiological,  both  of  which  have  re- 
ceived elaborate  treatment  by  Romanes. 

The  doctrine  of  geographical  isolation  offers  a  partial  ex- 
planation of  the  origin  of  the  peculiar  faun?e  and  florae  of 
remote  islands.  These  island  species,  however  peculiar, 
doubtless  came  originally  from  the  mainlands  where  their 
nearest  allies  now  occur;  thus  the  endemic  insects  of  the  Gala- 
pagos Islands  are  most  nearly  related  to  species  of  western 
South  America. 

The  first  individuals  of  Schisfoccrca  doubtless  reached  the 
Galapagos  Islands  by  means  of  the  wind  or  on  driftwood. 
These  individuals,  separated  from  the  main  body  of  their  spe- 
cies, would  interbreed  and  might  thereby  give  rise  to  a  new 
variety  or  species,  if  we  may  assume  that  the  average  of  charac- 
ters of  the  detached  portion  of  the  species  differed  from  that 
of  the  main  bodv  of  individuals ;  in  other  words,  that  the  iso- 


ORIGIN    OF    ADAPTATIONS    AND    OF    SPECIES  251 

lated  forms  varied  aroniul  a  mean  condition  of  their  own,  and 
no  longer  around  the  mean  of  the  species  as  a  whole. 

Besides  this,  the  influences  of  new  food  and  new  climatal  con- 
ditions as  means  of  modification  must  be  taken  into  account. 
Furthermore,  though  a  new  species  might  conceivalily  arise  on 
an  island  without  the  aid  of  natural  selection,  it  is  very  likely 
that  selection  has  often  played  a  part  in  the  formation  of  such 
a  species,  as  in  the  apterous  or  subapterous  forms  that  pre- 
dominate on  oceanic  islands.  While  it  is  possible  that  the 
earliest  arrivals  were  already  apterous,  and  arrived  safely  be- 
cause on  that  account  they  clung  to  driftwood  instead  of  flying 
away,  it  is  probable,  on  the  other  hand,  that  on  wind-swept 
islands  the  full-winged  and  more  \'enturesome  individuals 
would  be  carried  out  to  sea  and  drowned,  leaving  the  poorly 
winged  and  less  venturesome  ones  to  remain  and  transmit 
their  owni  life-saving  peculiarities ;  wdiich  would  become  inten- 
sified by  continual  selection  of  the  same  kind.  Romanes,  in- 
deed, regards  natural  selection  itself  as  but  one  form  of  iso- 
lation. 

Physiological  isolation,  which  though  important  will  not  be 
discussed  here,  "  arises  in  consequence  of  mutual  infertility 
between  the  members  of  any  group  of  organisms  and  those  of 
all  other  similarly  isolated  groups  occupying  simultaneously 
the  same  area."      (Romanes.) 


CHAPTER    VIII 

INSECTS    IN    RELATION    TO    PLANTS 

Insects,  in  common  with  other  animals,  depend  for  food 
primarily  upon  the  plant  world.  No  other  animals,  however, 
sustain  such  intimate  and  complex  relatiijns  to  plants  as  in- 
sects do.  The  more  luxuriant  and  varied  the  flora,  the  more 
abundant  and  diversified  is  its  accompanying  insect  fauna. 

Not  only  have  insects  become  profoundly  modified  for  using 
all  kinds  and  all  parts  of  plants  for  food  and  shelter,  but  plants 
themselves  have  been  modified  to  no  small  extent  in  relation  to 
insects,  as  appears  in  their  protective  devices  against  unwelcome 
insects,  in  the  curious  formations  known  as  '*  galls,"  the  various 
insectivorous  plants,  and  especially  the  omnipresent  and  often 
intricate  floral  adaptations  for  cross-pollination  through  the 
agency  of  insect  visitors.  Though  insects  have  laid  plants  un- 
der contribution,  the  latter  have  not  only  vigorously  sustained 
the  attack  but  have  even  pressed  the  enemy  into  their  own  ser- 
vice, as  it  were. 

Numerical  Relations. — The  number  of  insect  species  sup- 
ported by  one  kind  of  plant  is  seldom  small  and  often  surpris- 
ingly large.  The  poison  ivy  (Rhus  toxicodendron)  is  almost 
exempt  from  attack,  though  even  this  plant  is  eaten  by  a  leaf- 
mining  caterpillar,  two  pyralid  larvae  and  the  larva  of  a  scolytid 
beetle  ( Schwarz,  Dyar ) .  Horse-chestnut  and  buckeye  have  per- 
haps a  dozen  species  at  most ;  elm  has  eighty ;  birches  have  over 
one  hundred,  and  so  have  maples;  pines  are  known  to  harbor 
170  species  and  may  yield  as  many  more;  while  our  oaks  sus- 
tain certainly  500  species  of  insects  and  probably  twice  as  many. 
Turning  to  cultivated  plants,  the  clover  is  affected,  directly  or 
indirectly,  by  about  200  species,  including  predaceous  insects, 
parasites,  and  flower-visitors.     Clover  grows  so  vig'orously  that 

252 


INSECTS  IN  RELATION  TO  PLANTS  253 

it  is  able  to  withstand  a  great  deal  of  injury  from  insects.  Corn 
is  attacked  by  about  200  species,  of  which  50  do  notable  injury 
and  some  20  are  pests.     Aj^ple  insects  number  some  400  species. 

Not  uncommonly,  an  insect  is  restricted  to  a  single  species  of 
plant.  Thus  the  caterpillar  of  H codes  hypopliUcas  feeds  only 
on  sorrel  {Rmnex  acctoscUa) ,  so  far  as  is  known.  The  chry- 
somelid  Chrysochus  aurafiis  appears  to  l)e  limited  to  Indian 
hemp  {Apocymiin  androsccmifoliuiii)  and  to  milkweed  (As- 
clcpias).  In  many  instances,  an  insect  feeds  indifferently 
upon  several  species  of  plants  provided  these  have  certain 
attributes  in  common.  Thus  Argynnis  cyhclc,  aphrodite  and 
atlantis  eat  the  leaves  of  various  species  of  violets,  and  the 
Colorado  potato  beetle  eats  different  species  of  Solarium. 
Papilio  thoas  feeds  upon  orange,  prickly  ash  and  other  Ruta- 
cese.  Anosia  plexippus  eats  the  various  species  of  Asclepias 
and  also  Apocynuin  aiidrosccinifoliiuii ;  while  ChrysocJiiis 
also  is  limited  to  these  two  genera  of  plants,  as  was  said. 
These  plants  agree  in  having  a  milky  juice ;  in  fact  the  two 
genera  are  rather  nearly  related  botanically.  The  common  cab- 
bage butterfly  (Pier is  rapcc)  though  confined  for  the  most  part 
to  Cruciferae,  such  as  cabbage,  mustard,  turnip,  radish,  horse- 
radish, etc.,  often  develops  upon  Tropccoluui,  which  belongs  to 
Geraniace?e ;  all  its  food  plants,  however,  ha\-e  a  pungent  odor, 
which  is  probably  the  stimulus  to  oviposition. 

?^Iost  phytophagous  insects,  however,  range  over  many  food- 
plants.  The  cecropia  caterpillar  has  more  than  sixty  of  these, 
representing  thirty-one  genera  and  eighteen  orders  of  plants ; 
and  the  tarnished  plant  bug  (Lygits  prafciisis)  feeds  indiffer- 
ently on  all  sorts  of  herbage,  as  does  also  the  caterpillar  of 
Diacrisia  virgiriica.  Alany  of  the  insects  of  apple,  pear, 
quince,  plum,  peach,  and  other  plants  of  the  family  Rosaceas 
occur  also  on  wild  plants  of  the  same  family ;  and  the  worst  of 
our  corn  and  wheat  insects  have  come  from  wild  grasses.  As 
regards  number  of  food  plants,  the  gypsy  moth  "  holds  the 
record,"  for  its  caterpillar  will  eat  almost  any  plant.  In  Mass- 
achusetts, according  to  Forbush  and  Fernald,  it  fed  in  the  field 


254 


ENTOMOLOGY 


upon  78  Species  of  plants,  in  captivity  upon  458  species  (30 
under  stress  of  hunger,  the  rest  freely),  and  refused  only  19 
species,  most  of  which  (such  as  larkspur  and  red  pepper) 
had  poisonous  or  pungent  juices,  or  were  otherwise  unsuit- 

^  able  as  food.     The  migratorv 

FiG.  247.  .  .  .  ' 

locust  is  notoriously  omniv- 
orous, and  perhaps  eats  even 
more  kinds  of  plants  than  the 
gypsy  moth. 

Galls. — Alost  of  the  conspic- 
uous plant  outgrowths  known 
as    "  galls  "    are   made   by    in- 
sects,    though     many     of     the 
smaller   plant    galls    are   made 
by  mites  (Acarina)  and  a  few 
plant  excrescences  are  due  to 
nematode  worms  and  to  fungi. 
Among  insects, Cynipidse  (  Hy- 
menoptera)      are     pre-eminent 
as    gall-makers    and    next    to 
these,  Cecidomyiidje  (Diptera), 
Aphidid^e  and  Psyllidas  (Hemiptera)  ;  a  few  gall-insects  occur 
Fig.  248. 


Holciispis  globulus.  A,  galls  on  oak, 
natural  size;  B,  the  gall-maker,  twice 
natural   length. 


of  Ho  leas  pis   d\t 


on   oak.      Natural   size. 


among  Tenthredinid?e   (Hymenoptera)   and  Trypetid?e   (Dip- 
tera), and  one  or  two  among  Coleoptera  and  Lepidoptera. 
Cynipidje  affect  the  oaks  (Figs.  247,  248)   far  more  often 


INSECTS  IN  RELATION  TO  PLANTS 


255 


Fig.  249. 


than  any  other  plants,  though  not  a  few  species  select  the  wild 
rose.  Cecidomyiid  galls  occur  on  a  great  variety  of  plants,  and 
those  of  aphids  on  elm  (Fig.  249),  poplar,  and  many  other 
plants;  while  psyllid  galls  are  most  frequent  on  hackberry. 
The  galls  may  occur  anywhere  on  a  plant,  from  the  roots  to  the 
flowers  or  seeds,  though  each  gall-maker  always  works  on  the 
same  part  of  its  plant, — root,  stem, 
bud,  leaf,  leaf-vein,  flower,  seed,  etc. 

Galls  present  innumerable  forms, 
but  the  form  and  situation  of  a 
gall  are  usually  characteristic,  so 
that  it  is  often  possible  to  classify 
galls  as  species  even  before  the 
gall-maker  is  known. 

Gall-Making. — The  female  cy- 
nipid  punctures  the  plant  and  lays 
an  egg  in  the  wound ;  the  egg- 
hatches  and  the  surrounding  plant 
tissue  is  stimulated  to  grow  rapidly 
and  abnormally  into  a  gall,  which 
serves  as  food  for  the  larva ;  this 
transforms  within  the  gall  and  es- 
capes as  a  winged  insect.  The 
physiology  of  gall-formation  is  far 
from  being  understood.  It  has  been 
found  that  the  mechanical  irritation  from  the  ovipositor  is  not 
the  initial  stimulus  to  the  development  of  a  gall ;  neither  is 
the  fluid  which  is  injected  by  the  female  during  oviposition,this 
fluid  being  probably  a  lubricant ;  if  the  egg  is  removed,  the  gall 
does  not  appear.  Ordinarily  the  gall  does  not  begin  to  grow 
until  the  egg  has  hatched,  and  then  the  gall  grows  along  with 
the  larva;  exceptions  to  this  are  found  in  some  Hymenoptera 
in  which  the  egg  itself  increases  in  volume,  when  the  gall  may 
grow  with  the  egg.  It  appears  that  the  larva  exudes  some 
fluid  which  acts  upon  the  protoplasm  of  certain  plant  cells  (the 
cambium  and  other  cells  capable  of  further  growth  and  multi- 
plication) in  such  a  way  as  to  stimulate  their  increase  in  size 


i 

M^^Km^^ 

i 

JB 

i 

1 

i,.sy'^£ 

f 

^ 

^ 

Cockscomb  gall  of  Colopha  ulml 
on    elm.      Slightly    reduced. 


256  ENTOMOLOGY 

and  number.  \\'hy  the  gall  should  have  a  distinctive,  or  spe- 
cific, form,  it  is  not  yet  known.  There  is  no  evidence  that  the 
form  is  of  any  adaptive  importance,  and  the  subject  probably 
admits  of  a  purely  mechanical  explanation  —  a  problem  for  the 
future. 

Gall  Insects.  —  The  study  of  gall  insects  is  in  manv  respects 
difficult.  It  is  not  at  all  certain  that  an  insect  which  emerges 
from  a  gall  is  the  species  that  made  it ;  for  many  species,  even 
of  Cynipidse,  make  no  galls  themselves  but  lay  their  eggs  in 
galls  made  by  other  species.  Such  guest-insects  are  termed 
inquiUnes.  Furthermore,  both  gall-makers  and  inquilines  are 
attacked  by  parasitic  Hymenoptera,  making  the  interrelations 
of  these  insects  hard  to  determine.  Many  species  of  insects 
feed  upon  the  substance  of  galls;  thus  Sharp  speaks  of  as 
many  as  thirty  different  kinds  of  insects,  belonging  to  nearly 
all  the  orders,  as  having  been  reared  from  a  single  species  of 
gall. 

Parthenogenesis  and  Alternation  of  Generations. — Par- 
tlicnogcncsis  has  long  been  known  to  occur  among  Cynipidae. 
It  has  repeatedly  been  found  that  of  thousands  of  insects 
emerging  from  galls  of  the  same  kind,  all  were  females.  In 
one  such  instance  the  females  were  induced  by  Adler  to  lay  eggs 
on  potted  oaks,  when  it  was  found  that  the  resulting  galls  were 
quite  unlike  the  original  ones,  and  produced  both  sexes  of  an 
insect  which  had  up  to  that  time  been  regarded  as  another 
species.  Besides  parthenogenesis  and  this  alternation  of  gene- 
rations, many  other  complications  occur,  making  the  study  of 
gall-insects  an  intricate  and  highly  interesting  subject. 

Plant-Enemies  of  Insects. — ]\Iost  of  the  flowering  plants 
are  comparatively  helpless  against  the  attacks  of  insects,  though 
there  are  many  devices  which  prevent  "unwelcome  "  insects 
from  entering  flowers,  for  instance  the  sticky  calyx  of  the  catch- 
fly  (Silene  z'irginica) ,  which  entangles  ants  and  small  flies.  A 
few  plants,  however,  actually  feed  upon  insects  themselves. 
Thus  the  species  of  Drosera,  as  described  in  Darwin's  classic 
volume  on  insectivorous  plants,  have  specialized  leaves  for  the 


INSECTS  IN  RELATION  TO  PLANTS 


257 


purpose  of  catching  insects.  The  stout  hairs  of  these  leaves 
end  each  in  a  g-lolmlar  kiiol).  which  secretes  a  sticky  fluid. 
When  a  tly  ahglits  on  one  of  these  leaves  the  hairs  hend  over 
and  hold  the  insect:  then  a  fluid  analogotis  to  the  gastric  juice 
of  the  human  stomach  exudes,  digests  the 
alhuminoid  suhstances  of  the  insect  and  ''^'■-  --''"■ 

tliese  are  ahsorhed  into  the  tissues  of  the 
leaf;  after  which  the  tentacles  unfold 
and  are  ready  for  the  next  insect  \-isitor. 
The  Venus's  flytrap  is  another  well- 
known  example ;  the  trap.  f(jrmed  from 
the  terminal  portion  of  a  leaf,  consists  of 
two  valves,  each  of  which  hears  three 
trigger-like  hristles.  and  when  these  are 
touched  l)v  an  insect  the  \'ah'es  snap  to- 
gether and  fretjuently  imprison  the  insecc. 
which  is  eventually  digested,  as  hefore. 
In  the  common  pitcher-plants,  the  pitcher, 
fashioned  from  a  leaf,  is  lined  with  d(jwn- 
ward  pointing  bristles,  which  allow  an 
insect  to  enter  but  pre\ent  its  escape. 
The  bottom  of  the  pitcher  contains  water, 
in  which  ma}-  Ije  found  the  remains 
of  a  great  variety  of  insects  which 
ha\'e  drowned.  There  are  e\en  nectar 
glands  and  conspicuous  colors,  presum- 
ably to  attract  insects  into  these  traps, 
where  their  dec(jmp(jsition  products  are 
more    or    less    useful    to    the    plant.     In 


Fructifying  sprouts  of 
a  fungus,  Conlyccps  rav^:!- 
ncHi,  arising  from  the 
Ijody  of  a  white  grub, 
Lachnosterna.  Slightly 
reduced. — After   Riley. 


over    and     envelops     insects     that     have 

been  caught  by  the  glandular  hairs  of  the  upper  surface 
of  the  leaf,  a  copious  secretion  digests  the  softer  portions  of 
the  insects,  and  the  dissolved  nitrogenous  matter  is  absorbed 
into  the  plant.  Utricularia  has  little  bladders  which  entrap 
small  aquatic  insects.  These  plants  are  only  partially  depend- 
18 


258 


ENTOMOLOGY 


ent  on  insect-food,  however,  for  they  all  possess  chlorophyll. 

Bacteria  cause  epidemic  diseases  among-  insects,  as  in  the 
flacherie  of  the  silkworm ;  and  fungi  of  a  few  groups  are  spe- 
cially adapted  to  develop  in  the  bodies  of  living  insects. 

Those  who  rear  insects  know  how  frequently  caterpillars  and 
other  larvcT  are  destroyed  by  fungi  that  g*ive  the  insects 
a  powdered  appearance.  These  fungi,  referred  to  the  genus 
Isario,  are  in  some  cases  known  to  be  asexual  stages  of  forms 
of  Cordyccps,  which  forms  appear  from  the  bodies  of  various 
larvae,  pupae  and  imagines  as  long,  conspicuous,  fructifying 
sprouts  (Fig.  250). 

The  chief  fungus  parasites  of  insects  belong  to  the  large 
family  Entomophthoraceae,  represented  by  the  common  Empusa 
imtsccc    (Fig.   251)    which  affects   various   flies.      In  autumn, 

Fig.  251. 


Empusa  musca,  the  common  fly-fungus.  A,  house  fly  {Mttsca  domestica),  sur- 
rounded by  fungus  spores  (conidia) ;  B,  group  of  conidiophores  showing  conidia  in 
several  stages  of  development;  C,  basidium  (6)  bearing  conidium  (c)  before  discharge. 
B  and  C  after  Th.^xter. 

especially  in  warm  moist  weather,  the  common  house  fly  may 
often  be  seen  in  a  dead  or  dying  condition,  sticking  to  a  win- 
dow-pane, its  abdomen  distended  and  presenting  alternate  black 
and  white  bands,  while  around  the  fly  at  a  little  distance  is  a 


INSECTS  IN  RELATION  TO  PLANTS  259 

wliite  powdery  rinj;',  nv  halo.  'Hie  white  intersegmental  bands 
are  made  bv  threads  of  tlie  fnni^iis  just  name(b  and  the  white 
halo  by  countless  asexual  spores  known  as  coiiiilia,  which  have 
been  forcibly  discharged  from  the  swollen  threads  that  bore 
them  (  h'ig.  -'51  )  by  pressure,  resulting  probably  from  the  ab- 
sorption of  moisture.  These  spores,  ejected  in  all  directions, 
may  infect  another  fly  upon  contact  and  produce  a  grow'th  of 
fungus  threads,  or  liyl^luc,  in  its  body.  The  fungus  may  be 
])r(~»pagated  also  by  means  of  resting  spores,  as  found  by  Thax- 
ter.  t)ur  authority  upon  the  fungi  of  insects. 

Eiiipiisa  aphidis  is  very  common  on  plant  lice  and  is  an  im- 
portant check  upon  their  multiplication.  Aphids  killed  by  this 
fungus  are  found  clinging  to  their  food  plant,  with  the  body 
swollen  and  discolored.  Einpusa  grylli  attacks  crickets,  grass- 
hoppers, caterpillars  and  other  forms.  Curiously  enough, 
grasshoppers  affected  by  this  fungus  almost  always  crawl  to 
the  top  of  some  plant  and  die  in  this  conspicuous  position. 

Sporotrichuni,  a  genus  of  hyphomycetous  fungi,  affects  a 
great  variety  of  insects,  spreading  within  the  body  of  the  host 
and  at  length  emerging  to  form  on  the  body  of  the  insect  a 
dense  white  felt-like  covering,  this  consisting  chiefly  of  myriads 
of  spores,  by  means  of  which  healthy  insects  may  become  in- 
fected. Under  favorable  conditions,  especially  in  moist  sea- 
sons, contagious  fungus  diseases  constitute  one  of  the  most 
important  checks  upon  the  increase  of  insects  and  are  therefore 
of  vast  economic  importance.  Thus  the  termination  (in 
1889)  of  a  disastrous  outlireak  of  the  chinch  bug'  in  Illinois 
and  neighboring  states  "  was  apparently  due  chiefly,  if  not 
altogether,  to  parasitism  by  fungi."  Artificial  cultures  of  the 
common  Sporofrichnm  globiilifcnim  have  been  used  exten- 
sively as  a  means  of  spreading  infection  among  chinch  bugs 
and  grasshoppers,  with,  however,  Imt  moderate  success  as  yet. 

Insects  in  Relation  to  Flowers. — Among  the  most  marve- 
lous phenomena  known  to  the  biologist  are  the  innumerable 
and  complex  adaptations  by  means  of  which  flowers  secure 
cross    pollination    through     the    agency    of    insect    visitors. 


26o 


ENTOMOLOGY 


Cross  fertilization  is  actually  a  necessity  for  the  continued 
vigor  and  fertility  of  flowering  plants,  and  while  some  of  them 
are  adapted  for  cross  pollination  by  wind  or  water,  the  major- 
ity of  flowering-  plants  exhil)it  profound  modifications  of  floral 
structure  for  compelling  insects  ( and  a  few  other  animals,  as 
birds  or  snails)  to  carry  pollen  from  one  flower  to  another.  In 
general,  the  conspicuous  colors  of  flowers  are  for  the  purpose 

Fig.  252. 


Bumble    bee    (Boiiibus)    entering    flower    of    blue-fiag    il ris    -versicolor). 
reduced. 


of  attracting  insects,  as  are  also  the  odors  of  flowers.  Night- 
blooming  flowers  are  often  white  or  yellow  and  as  a  rule 
strongly  scented.  Colors  and  odors,  however,  are  simply 
indications  to  insects  that  edible  nectar  or  pollen  is  at  hand. 
Such  is  the  usual  statement,  and  it  is  indeed  probable  that 


INSECTS  IN  RELATION  TO  PLANTS 


261 


Fig.  253. 


insects  actually  do  associate  color  and  nectar,  even  though 
thev  will  tl}'  to  bits  of  colored  paper  almost  as  readilv  as  they 
will  to  tlowers  of  the  same  colors.  Jt  is  not  to  be  supposed, 
however,  that  insects  realize  that  they  confer  any  benefit 
ujion  the  plant  in  the  flowers  of  which  they  find  food.  At 
an\'  rate,  most  flowers  are  so 
constructed  that  certain  insects 
cannot  get  the  nectar  or  pollen 
without  carrying  some  pollen 
away,  and  cannot  enter  the  next 
flower  of  the  same  kind  without 
leaving  some  of  this  pollen  upon 
the  stigma  of  that  flower.  Take 
the  iris,  for  example,  which  is 
admirably  adapted  for  pollina- 
tion by  a  few  bees  and  flies. 

Iris. — In  the  common  blue-flag  (Iris  versicolor, 
Fig.  252),  each  of  the  three  drooping  sepals  forms 
the  floor  of  an  arched  passageway  leading  to  the  nec- 
tar. Over  the  entrance  and  pointing  outward  is  a 
movable  lip  (Fig.  253,  /),  the  outer  surface  of  which 
is  stigmatic.  An  entering  bee  hits  and  bends  down 
the  free  edge  of  this  lip,  wdiich  scrapes  pollen  from 
the   back   of   the   insect   and    then    springs   Ijack    into 

place.  Within    the      passage,    the        section   to  illustrate  cross   pollination 

hairy  back  of  the  bee  rubs  against    °'  -'"'■  ""'  ^"''^^;"=  ^'  ^'*^™^'^'^  '''' 

J  "-'  n,  nectary;   s,  sepal. 

an  overhanging  anther  (a/;)    and 

becomes  powdered  with  grains  of  pollen  as  the  insect  pushes 
down  towards  the  nectar.  As  the  bee  backs  out  of  the  pass- 
age it  encounters  the  guardian  lip  again,  but  as  this  side  of 
the  lip  can  not  receive  pollen,  immediate  close  pollination  is 
prevented.  Of  course,  it  is  possible  for  bees  to  enter  another 
part  of  the  same  flower  or  another  flower  of  the  same  plant, 
l)ut  as  a  matter  of  fact,  they  habitually  fly  away  to  another 
plant ;  moreover,  as  Darwin  found,  foreign  pollen  is  prepotent 
over  pollen  from  the  same  flower.      It  may  be  added  that  bees 


262 


ENTOMOLOGY 


and  other  poUenizing  insects  ordinarily  visit  in  succession  sev- 
eral flowers  of  the  same  kind. 

Orchids. — The  orchids,  with  their  fantastic  forms,  are  really 
elaborate  traps  to  insure  cross  pollination.  In  some  orchids 
{Hahcnaria  and  others)  the  nectar,  lying-  at  the  bottom  of  a 
long  tube,  is  accessible  only  to  the  long-tongued  Sphingid?e. 
While  probing  for  the  nectar,  a  sphinx  moth  brings  each  eye 
against  a  sticky  disk  to  which  a  pollen  mass  is  attached,  and 
flies  away  carrying  the  mass  on  its  eye.  Then  these  poUinia 
bend  down  on  their  stalks  in  such  a  way  that  when  the  moth 
thrusts  its  head  into  the  next  flower  they  are  in  the  proper 
position  to  encounter  and  adhere  to  the  stigina.  The  orchid 
Angrcrcuiu  scsquipcdalc,  of  Madagascar,  has  a  nectary  tube 
more  than  eleven  inches  long,  from  which  Darwin  inferred  the 
existence  of  a  sphinx  moth  with  a  tongue  equally  long, — an 
inference  which  proved  to  be  correct. 

Milkweed. — The  various  milkweeds  are  fascinating  subjects 
to  the  student  of  the  interrelations  of  flowers  and  insects.  The 
flowers,   like  those  of  orchids,   are   remarkablv   formed   with 


Fig.  254. 


^^ 


Structure  of  milkweed  flower  (Asclcpuis  incaniata)  with  reference  to  cross  pollina- 
tion. A,  a  single  flower;  c,  corolla;  li,  hood;  B.  external  aspect  of  fissure  (/)  leading 
up  to  disk  and  also  into  stigmatic  chamber;   /;,   hood;   C,  pollinia;   d,  disk.      Enlarged. 


INSECTS  IN  RELATION  TO  PLANTS 


^63 


reference  to  cross  pollination  by  insects.  As  a  honc}-  bee  or 
other  insect  crawls  o\-er  the  Howers  (hii^'.  254,  A)  to  get  the 
nectar,  its  le.^'s  slip  in  between  the  pecnliar  nectariferons  Iioods 
sitnated  in  front  of  each  (?/;///('/'.  As  a  let;"  is  drawn  npwarcl  one 
of  its  claws,  hairs,  or  spines  frecinently  catches  in  a  \'-shaped 
fissnre  (/,  Fig".  254,  B)  and  is  guided  along  a  slit  to  a  notched 
disk,  or  corpuscle  ( iMg.  254,  C,  </ ) .  This  disk  clings  to  the 
leg  of  the  insect,  which  carries  off  by  means  of  the  disk  a  pair 
of  pollen  masses  of  poUinia  (Fig.  254,  C).  When  first  re- 
moved from  their  enclosing  pockets,  or  anthers,  these  thin 
spatulate  pollinia  lie  each  pair  in  the  same  plane,  but  in  a  few 
minutes  the  two  pollinia  twist  on  their  stalks  and  come  face  to 
face  in  such  a  way  that  one  of  them  can  be  easily  introduced 
into  the  sfigiiiatic  chamber  of 
a  new  flower  \'i sited  bv  the  in- 


FiG.  2s=;. 


A  wasp,  Splicx  ichncuDioiica, 
linia  of  milkweed  attached  to 
Slightly  enlarged. 


ith   pel- 
ts   legs. 


the  insect  ordinarily  break  the 

stem,    or    rcfinaciilitiii,    of    the 

pollinium  and   free  the  insect. 

Often,  however,  the  insect  loses 

a    leg   or   else    is    permanently 

entrapped,    particularly    in    the 

case     of     such     large-flowered 

milkweeds  as  Asclcpias  coriiiiti, 

wdiich  often  captures  bees,  flies 

and  moths  of  considerable  size. 

Pollination  is  accomplished  by 

a  great  variety  of  insects,  chiefly  Hymenoptera,  Diptera,  Lepi- 

doptera  and  Coleoptera.     These  insects  when  collected  about 

milkweed  flow^ers  usually  display  the  pollinia  dangling  from 

their  legs,  as  in  Fig.  255. 

The  details  of  pollination  may  lie  g'athered  bv  a  close  ob- 
ser^'er  from  observations  in  the  field  and  may  be  demonstrated 
to  perfection  by  using  a  detached  leg  of  an  insect  and  dragging 
it  upward  between  two  of  the  hoods  of  a  flower ;  first  to  re- 
move the  pair  of  pollinia  and  then  again  to  introduce  one  of 
them  into  an  empty  stigmatic  chamber. 


264 


ENTOMOLOGY 


Yucca. — An  extraordinary  example  of  the  interdependence 
of  plants  and  insects  was  made  known  by  Riley,  whose 
detailed  account  is  here  summarized.  The  yuccas  of  the 
southern  United  States  and  ^Mexico  are  among  the  few  plants 
that  depend  for  pollination  each  upon  a  single  species  of  insect. 
The  pollen  of  Yucca  iilamciifosa  cannot  be  introduced  into  the 
stigmatic  tube  of  the  flower  without  the  help  of  a  little  white 
tineid  moth,  Pronuba  ynccasclla,  the  female  of  which  pollen- 
izes  the  flower  and  lays  eggs  among  the  ovules,  that  her  larvae 


Fig.  256. 


may  feed  upon  the 
young  seeds.  \Miile 
the  male  has  no  un- 
usual structural  pecu- 
liarities, the  female  is 
adapted  for  her  special 
work  by  modifications 
which  are  u  n  i  q  u  e 
a  m  o  n  g  Lepidoptera, 
namely,  a  pair  of  pre- 
hensile and  spinous 
maxillary  "  tentacles  " 
(Fig.  256,  A)  and  a 
long  protrusible  ovi- 
positor (B)  which 
combines  in  itself  the 
functions  of  a  lance 
and  a  saw. 

The  female  begins  to  work  soon  after  dark,  and  will  con- 
tinue her  operations  even  in  the  light  of  a  lantern.  Clinging 
to  a  stamen  (Fig.  257)  she  scrapes  off  pollen  with  her  palpi 
and  shapes  it  into  a  pellet  by  using  the  front  legs.  After 
gathering  pollen  from  several  flowers  she  flies  to  another 
flower,  as  a  rule,  thrusts  her  long  flexible  ovipositor  into  the 
ovary  (Fig.  258)  and  lays  a  slender  egg  alongside  seven  or 
eight  of  the  ovules. 


Pronuba  yuccasella.'  A,  maxillary  tentacle 
and  palpus;  B,  ovipositor. — After  Riley.  Fig- 
ures 256-258  are  republished  from  the  Third 
Report  of  the  Missouri  Botanical  Garden,  by 
permission. 


INSECTS    IN    RELATION    TO    PLANTS 


>65 


the  pistil  and  actually  thrusts  pollen  into  the  stigmatic  tube  and 
pushes  it  in  firmly.  The  ovules  develop 
into  seeds,  some  of  which  are  consumed 
by  the  larv;e.  thoug-h  plenty  are  left  to 
perpetuate  the  plant  itself.  Three  species 
of  Pronuba  are  known,  each  restricted 
to  particular  species  of  Yucca.  Rilc)' 
says  that  Yucca  never  produces  seed 
where  Prouuha  does  nt)t  occur  or  where 
she  is  excluded  artificially,  and  that 
artificial  pollination  is  rarely  so  success- 
ful as  the  normal  method. 

Why  does  the  insect  do  this?  The  lit- 
tle nectar  secreted  at  the  base  of  the  pistil 
appears  to  be  of  no  consequence,  at  pres- 
ent, and  the  stigmatic  fluid  is  not  necta- 
rian ;  indeed,  the  tongue  of  Pronuba,  used 
in  clinging  to  the  stamen,  seems  to  have 
lost  partially  or  entirely  its  sucking  power, 
and  the  alimentarv  canal  is  resrarded  as  functionless 


Pronuba  yuccasella,  fe- 
male, gathering  pollen 
from  anthers  of  Yucca. 
Enlarged. 

Ordina- 


Pronuba  moth  ovipositing  in   flower  of   Yucca.      Slightly   reduced. 


rily  it  is  the  flower  which  has  become  adapted  to  the  insect, 
which  is  enticed  by  means  of  pollen  or  nectar,  but  here  is  a 


266 


ENTOMOLOGY 


flower  which — though  entomophilous  in  general  structure— has 
apparently  adapted  itself  in  no  way  to  the  single  insect  upon 
which  it  is  dependent  for  the  continuance  of  its  existence.  More 
than  this,  the  insect  not  only  lal3ors  without  compensation  in  the 
way  of  food,  but  has  even  become  highly  modified  with  refer- 
ence to  the  needs  of  the  plant, — its  special  modifications  being 
unparalleled  among  insects  with  the  exception  of  bees,  and 
being  more  puzzling  than  the  more  extensive  adaptations  of 
the  bees  wdien  we  take  into  consideration  the  impersonal  nature 
of  the  operations  of  Pronuba.  Further  investigation  may 
render  these  extraordinary  interrelations  more  intelligible,  or 
less  mysterious,  than  they  are  at  present. 

The  bogus  Yucca  moth 
Fig.  259.  {Prodoxus    qitiiiqiicpinic- 

fclla)  closely  resembles 
and  associates  with  Pro- 
uuha  but  oviposits  in  the 
flower  stalks  of  Yucca 
and  has  none  of  the  spe- 
cial adaptive  structures 
found  in  Pronuba. 

As  regards  floral  adap- 
tations, these  examples 
are  sufficient  for  present 
purposes ;  many  others 
have  been  described  l)y 
the  botanist ;  in  fact,  the 
adaptations  for  cross  pol- 
lination by  insects  are  as 
varied  as  the  flowers  them- 
selves. 
Insect  Pollenizers. — The  great  majority  of  entomophilous 
flowers  are  pollenized  by  bees  of  various  kinds ;  the  apple, 
pear,  blackberry,  raspberry  and  many  other  rosaceous  plants 
depend  chiefly  upon  the  honey  bee,  while  clover  cannot  set  seed 
without  the  aid  of  Immble  bees  or  honey  bees,  assisted  possibly 


Phlcgcthontius   sc.vta   visiting   flower   of   Pi- 
Reduced. 


INSECTS    IN    RELATION    TO    I'EANTS 


267 


l)v  Ituttcrflies.  I^ilies  and  orcliids  trccinently  em])l(>y  l)utternics 
and  moths,  as  well  as  l)ees.  and  the  milkweed  is  adapted  in  a 
remarkal)le  manner  for  pollination  l)y  1)ntternies,  moths  and 
some  wasps,  as  was  descrihed.  Honeysuckle,  lilac,  azalea, 
tohacco,  l\'hnil(i,  Pulurn  and  many  other  strctnt^ly  scented  anrl 
conspicuous  nocturnal  llowers  attract  for  their  own  uses  the 

Fig.  260. 


A   buttcrily,   Fulitcs  pcckiiis,   stealing   nectar   from   a   flower   of  Iris  z'crsicolor. 
Slightly  reduced. 


long-tonged  sphinx  moths  (Fig.  259)  ;  the  evening  primrose, 
like  milkweed,  is  a  favorite  of  noctuid  moths.  Umhelliferous 
plants  are  pollenized  chietiy  by  various  flies,  but  also  by  bees 
and  wasps.  Pond  lilies,  golden  rod  and  some  other  flowers 
are  pollenized  largely  by  beetles,  though  the  flowers  exhibit  no 
special  modifications  in  relation  to  these  particular  insects.      It 


268 


ENTOMOLOGY 


Fig.  261 


is  noteworthy  that  polHnation  is  performed  only  by  the  more 
highly  organized  insects,  the  bees  heading  the  list. 

Of  all  the  insects  that  haunt  the  same  flower,  it  frequently 
happens  that  only  a  few  are  of  any  use  to  the  flower  itself ; 
many  come  for  pollen  only;  many  secure  the  nectar  illegiti- 
mately ;  thus  bumble  bees  puncture  the  nectaries  of  columbine, 
snapdragon  and  trumpet  creeper  from  the  outside,  and  wasps 
of  the  genus  Odyiicnis  cut  through  the  corolla  of  Pcntstcuwn 
ItTZ'igafus,  making  a  hole  opposite  each  nectary ;  then  there  are 
the  many  insects  that  devour  the  floral  organs,  and  the  insects 
which  are  predaceous  or  parasitic  upon  the  others.  In  the 
Iris,  according  to  Needham,  two  small  bees  (Clisodon  tcrmi- 
luilis  and  Osniia  disfiucta)  are  the  most  important  pollenizers, 
and  next  to  them  a  few  syrphid  flies,  while  bumble  bees  also 

are  of  some  impor- 
tance. The  beetle 
Trie  hilts  pigcr  and  sev- 
eral small  flies  obtain 
pollen  without  assist- 
ing the  plant,  and 
Painplula,  Eudauius, 
Chrysophanus  a  n  d 
some  other  butterflies 
succeed  after  many 
trials  in  stealing  the 
nectar  from  the  out- 
side (Fig.  260).  A 
weevil  (Moiioiiychus 
z'lilpcciiliis)  punctures 
the  nectary,  and  the 
flowing  nectar  then  at- 
tracts a  great  variety  of 
insects.  Grasshoppers 
and  caterpillars  eat  the 
flowers,  an  ortalid  fly  destroys  the  buds,  and  several  parasitic 
or  predaceous  insects  haunt  the  plant ;  in  all,  over  sixty  species 
of  insects  are  concerned  in  one  way  or  another  with  the  Iris. 


A,  right  mandible;  B,  right  maxilla;  C,  hypo- 
pharynx,  of  a  pollen-eating  beetle,  Euphoria  inda. 
Enlarged.  (The  mandibles  are  remarkable  in 
being  two-lobed.) 


INSECTS  IN  RELATION  TO  PLANTS 


269 


Modifications  of  Insects  with  Reference  to  Flowers. — 

While  the  manifold  and  ex(|nisite  adaptations  of  tlie  dower  for 
eross  pollination  have  eni^aj^ed  nniversal  attention,  very  little 
has  heen  recorded  concernin_^'  the  adaptations  of  insects  in  re- 
lation   to    tlowers.      in    fact,    the   adapta- 

11  •  1     1       ,1  1  ^'  "■•  -6-- 

tion    IS    larg'ely   one-sided;    tlowers    ha\e 

lieconie  adjusted  to  the  structure  of  in- 
sects as  a  matter  of  \-ital  necessity — to 
init  it  that  way — while  insects  have  had 
no  such  urgent  need — so  to  speak — in 
relation  to  floral  structure.  Thev  ha\-e 
been  induenced  by  floral  structure  to 
soiue  extent,  however,  and  in  some  cases 
to  a  \-ery  great  extent,  as  appears  from 
their  structural  and  i)hysiological  adapta- 
tions for  gathering  and  using  pollen  and 
nectar. 

Among  mandibulate  insects,  beetles 
and  caterpillars  that  eat  the  floral  en- 
velopes show'  no  special  modifications 
for  this  purpose ;  pollen-feeding  beetles, 
however,  usually  have  the  mouth  parts 
densely  clothed  with  hairs,  as  in  Euphoria  (Fig.  261).  In 
suctorial  insects,  the  mouth  parts  are  frequently  formed  with 
reference  to  floral  structure ;  this  is  the  case  in  many  but- 
terflies and  particularly  in  Sphingid?e,  in  which  the  length  of 
the  tongue  bears  a  direct  relation  to  the  depth  of  the  nectary  in 
the  flowers  that  they  visit.  According  to  ]\Iiiller,  the  mouth 
parts  of  Syrphidae,  Stratyomyiid?e  and  Aluscicte  are  specially 
adapted  for  feeding  on  pollen.  In  Apidse,  the  tongue  as  com- 
pared wdth  that  of  other  Hymenoptera,  is  exceptionally  long, 
enabling  the  insect  to  reach  deep  into  a  flower,  and  is  exqui- 
sitely specialized  (Fig.  127)  for  lapping  up  and  sucking  in 
nectar. 

Pollen-gathering  flies  and  bees  collect  pollen  in  the  hairs  of 
the  body  or  the  legs;  these  hairs,  especially  dense  and  often 


Pollen-gathering  hair 
from  a  worker  honey 
bee,  with  a  pollen  grain 
attached.  Greatly  mag- 
nified. 


2/0 


ENTOMOLOGY 


twisted  or  branched  (Figs.  262,  89)  to  hold  the  pollen,  do  not 
occur  on  other  than  pollen-gathering  species  of  insects.  Caii- 
dell  found  that  out  of  200  species  of  Hymenoptera  only  22, 
species  had  branched  hairs  and  that  these  species  belonged 
without  exception  to  the  pollen-gathering  group  Anthophila, 


Adaptive  modifications  of  the  legs  of  the  worker  honey  bee.  A,  outer  aspect  of 
left  hind  leg;  B,  portion  of  left  middle  leg;  C,  inner  aspect  of  tibio-tarsal  region  of 
left  hind  leg;  D,  tibio-tarsal  region  of  left  fore  leg;  a,  antenna  comb;  h,  brush;  c, 
coxa;  CO,  corbiculum;  /,  femur;  pc,  pollen  combs;  s.  spur;  sp,  spines;  ss,  spines;  t, 
trochanter;  t\,  tibia;  v,  velum;  w,  wax  pincers;  /-5,  tarsal  segments;  /,  metatarsus, 
or  planta. 

no  representative  of  which  was  found  without  such  hairs. 
Similar  branched  hairs  occur  also  on  the  flower-frequenting 
Bombyliidae  and  Syrphidas. 

The  most  extensive  modifications  in  relation  to  flowers  are 
found  in  Proiiuba,  as  already  described,  and  above  all  in 
Apidse,  especially  the  honey  bee. 

Honey  Bee. — The  thorax  and  abdomen  and  the  bases  of  the 
legs   are   clothed   with    flexible   branching  hairs    (Fig.   262), 


INSECTS  IN  RELATION  TO  PLANTS  27 1 

which  entangle  pollen  grains.  These  are  comhed  ont  of  the 
gatliering  hairs  hy  means  of  special  pollen  combs  (  JMg.  263, 
C.f^c)  on  the  inner  snrface  of  the  proximal  segment  of  the  hind 
tarsus,  the  middle  legs  also  assisting  in  this  operation.  JM-om 
these  comhs,  the  pollen  is  transferred  to  the  pollen  boskets,  or 
corbicula  (Fig.  263,  A,  co) ,  of  the  outer  surface  of  each  hind 
tihia ;  hy  crossing  the  legs,  the  pollen  from  one  side  is  trans- 
ferred to  the  corhiculum  of  the  opposite  side,  the  spines  (ss)  on 
the  posterior  margin  of  the  tihia  serving-  to  scrape  the  pollen 
from  the  coml)S.  Arri\-ing  at  the  nest,  the  hind  legs  are  thrust 
into  a  cell  and  the  mass  of  pollen  on  each  corhiculum  is  pried 
out  hy  means  of  a  spur  situated  at  the  apex  of  the  middle  tiljia 
(  iMg.  263,  B,  s),  this  lever  heing  slipped  in  at  the  upper  end 
of  the  corhiculum  and  then  pushed  along  the  tibia  under  the 
mass  of  pollen  ;  the  spur  is  used  also  in  cleaning  the  wings, 
which  explains  its  presence  on  queen  and  drone,  as  well  as 
worker,  but  the  pollen-gathering  structures  of  the  hind  legs 
are  confined  to  the  worker.  This  is  true  also  of  the  lea.v- 
piiiccrs  of  the  hind  legs  (Fig.  263,  A,  C,  w)  at  the  tibio-tarsal 
articulation ;  these  nippers  are  used  l)y  the  worker  to  remove 
the  wax  plates  from  the  al)domen. 

For  cleaning  the  antenn.'e,  a  front  leg-  is  passed  over  an 
antenna,  which  slips  into  a  semicircular  scraper  (Fig.  263, 
D,  a)  fashioned  from  the  basal  segment  of  the  tarsus;  when 
the  leg  is  bent  at  the  tibio-tarsal  articulation,  an  appendage,  or 
z'cliim  [z'),  of  the  tibia  falls  into  place  to  complete  a  circular 
comb,  through  which  the  antenna  is  drawn.  This  comb  is 
itself  cleaned  by  means  of  a  brush  of  hairs  (b)  on  the  front 
margin  of  the  tibia.  A  series  of  erect  spines  (sp)  along  the 
anterior  edge  of  the  metatarsus  is  used  as  an  eye  brush,  to 
remove  pollen  grains  or  other  foreign  bodies  from  the  hairs 
of  the  compound  eyes.  The  labium,  hypopharynx  and  max- 
\\\x  (Fig.  54)  are  exquisitely  constructed  with  reference  to 
gathering  and  sucking  nectar ;  the  maxilhe  are  used  also  to 
smooth  the  cell  walls  of  the  comb;  the  mandibles  (Fig.  45,  C). 
notched  in  queen  and  drone  but  with  a  sharp  entire  edge  in  the 


2^2 


ENTOMOLOGY 


worker,  are  used  for  cutting,  scraping  and  moulding  wax,  as 
well  as  for  other  purposes.  The  entire  digestive  system  of  the 
honey  bee  is  adapted  in  relation  to  nectar  and  pollen  as  food ; 
the  pro\-entriculus  forms  a  reservoir  for  honey  and  is  even 
provided  at  its  mouth  with  a  rather  complex  apparatus  for 
straining  the  honey  from  the  accompanying'  pollen  grains,  as 
described  hy  Cheshire.  The  wax  glands  (Fig.  102)  are  re- 
markable specializations  in  correlation  with  the  food  habits,  as 
are  also  the  various  cephalic  glands,  the  chief  functions  of 
which  are  given  as :  ( i )  digestion,  as  the  conversion  of  cane 
sugar  into  grape  sugar,  and  possibly  starch  into  sugar;  (2) 
the  chemical  alteration  of  wax;  (3)  the  production  of  special 
food  substances,  which  are  highly  important  in  larval  develop- 
ment. 

Numerous  special  sensory  adaptations  also  occur.  In  fact, 
the  whole  organization  of  the  honey  bee  has  become  pro- 
foundly modified  in  relation  to  nectar  and  pollen.  Many 
other  insects  have  the  same  food  but  none  of  them  sustain  such 
intimate  relations  to  the  flowers  as  do  the  bees. 

Ant-Plants. — There  are  several  kinds  of  tropical  plants 
Avhich  are  admirably  suited  to  the  ants  that  inhabit  them.  In- 
deed, it  is  often  asserted  that  these  plants  have  become  modified 

Fig.  264. 


Acacia  spha:rocc\mala,  an  ant-plant,  h.  one  of  the  "  Helt's  bodies";  g.  gland;  s,  .>, 
■hollow  stipular  thorns,  perforated  by  ants.  Reduced. — From  Strasburger's  Lchrbuch 
dcr  Botanik. 


INSECTS  IN  RELATION  TO  PLANTS 


273 


with  special  reference  to  their  use  Ijy  ants,  ihouqh  tliis  is  a 
gTatuitous  and  improbable  assumption. 

Belt  found  several  species  of  Acacia  in  Xicaras^na  and  the 
Amazon  \-alley  which  ha\e  laro-e  hollow  slipular  thorns,  in- 
habited by  ants  of  the  g-enus  Psciidoniyniia.  I'hc  ants  enter 
by  boring"  a  hole  near  the  a])ex  of  a  thorn  (  l^^ig.  264,  .v).  The 
plant  affords  the  ants  food  as  well  as  shelter,  for  glands  {i^) 


Fig.  265. 


Fig.  266. 


Portion  of  young  stem  of  Cccrofia  odoiol^iis, 
showing  internodal   pits,   a  and   b.     Natural  size. 

Figures  265-267  are  from  Schimper's  Fflanzcn- 
gcograpTuc. 


Cccrofia  adcnopns.  Por- 
tion of  a  stem,  split  so  as 
to  show  internodal  cham- 
bers and  the  intervening 
septa  perforated  by  ants. 


at  the  bases  of  the  petioles  secrete  a  sugary  fluid,  while  many 
of  the  leaflets  are  tipped  with  small  egg-shaped  or  pear-shaped 
appendages  (b)  known  as  "  Belt's  bodies,"  which  are  rich  in 
albumin,  fall  ofl^  easily  at  a  touch,  and  are  eaten  by  the  ants. 
These  ants  drive  away  the  leaf-cutting  species,  incidentally 
protecting  the  tree  in  which  they  live. 
19 


274 


ENTOMOLOGY 


The  ant-trees   (Cccropia  adcnopus)   of  Brazil  and  Central 
America   have  often   been   referred   to   by   travelers.      When 
one  of  these  trees  is  handled  roughly,  hosts  of  ants  rush  out 
P        ,_  from  small  openings  in  the 

stems  and  pugnaciously  at- 
tack the  disturber.  Just 
above  the  insertion  of  each 
leaf  is  a  small  pit  (Fig.  265, 
a,  b)  where  the  wall  is  so 
thin  as  to  form  a  mere  dia- 
phragm, through  which  an 
ant  (probably  a  fertilized 
female)  bores  and  reaches  a 
hollow  internode.  To  es- 
tablish communication  Ije- 
tween  the  internodal  cham- 
bers, the  ants  bore  through 
the  intervening  septa  (Fig. 
266).  They  seldom  leave 
the  Cccropia  plant,  unless 
disturbed,  and  even  keep 
herds  of  aphids  in  their 
abode.  The  base  of  each 
petiole  bears  (Fig.  267)  tender  little  egg-like  bodies  ("  ]\Iul- 
ler's  ])odies  ")  which  the  ants  detach,  store  away  and  eat; 
the  presence  of  these  bodies  is  a  sure  sign  that  the  tree  is  un- 
inhabited by  these  ants,  which,  by  the  way,  belong  to  the  genus 
A:::fcca. 

It  is  too  much  to  assert  that  the  ants  protect  the  Cccropia 
plant  /;/  return  for  the  food  and  shelter  which  they  obtain. 
All  ants  are  hostile  to  all  other  species  of  ants,  with  few  excep- 
tions, and  even  to  other  colonies  of  their  own  species;  so  that 
their  assaults  upon  leaf-cutting  ants  are  by  no  means  special 
and  adaptive  in  their  nature,  and  any  protection  that  a  plant 
derives  thereby  is  merely  incidental.  Furthermore,  hollow 
stems,  glandular  petioles  and  pitted  stems  are  of  common  oc- 


Cccropia  adoiopus.     Base  of   petiole  showing 
"  Miiller's    bodies."      Slightly    reduced. 


INSECTS  IN  RELATION  TO  PLANTS 


275 


currence  wlien  they  bear  no  relation  to  the  needs  of  ants. 
These  interrelations  oi  ants  and  plants  are  too  often  misinter- 
preted in  popular  and  uncritical  accounts  of  the  subject. 

The  interesting;-  habits  of  the  leaf-cuttiui;-  ants  in  relation  to 
the  plants  that  they  attack  are  described  in  a  subsequent  chap- 
ter, where  will  be  found  also  an  account  of  the  harvesting?-  ants. 


.'oS. 


HyJiu'tliyti 


Dwntanitm.      Section  of  pseudo-bulb,  to  show  chamber 
One    fourth    natural    size. — After    Forel. 


inhabited  by  ants. 


The  epiphytic  plants  Mynitccodia  and  Hydnopliytuui,  of 
Java,  form  spongy  bulb-like  masses,  the  chambers  of  which 
are  usually  tenanted  by  ants,  which  rush  forth  when  disturbed. 
These  lumps  (Fig.  268)  are  primarily  water-reservoirs,  but 
the  ants  utilize  them  by  boring  into  them  and  from  one  cham- 
ber into  another.  In  plants  of  the  genus  Huniholdtia  the  ants 
can  enter  the  hollow  internodes  through  openings  that  already 
exist. 


CHAPTER    IX 

INSECTS    IN    RELATION    TO    OTHER   ANIMALS 

I.    The  General  Subject 

On  the  one  hand,  insects  may  derive  their  food  from  other 
animals,  either  hving'  or  dead :  on  the  other  hand,  insects  them- 
selves are  food  for  other  animals,  especially  fishes  and  birds, 
against  which  they  protect  themselves  by  various  means,  more 
or  less  effective.  These  topics  form  the  principal  subject  of 
the  present  chapter. 

Predaceous  Insects. — Innumerable  aquatic  insects  feed 
largely  or  entirely  upon  microscopic  Protozoa,  Rotifera,  Ento- 
mostraca.  etc. ;  this  is  especially  the  case  with  culicid  and  chi- 
ronomid  larvae.  Many  aquatic  Hemiptera  and  Coleoptera 
prey  upon  planarians,  nematodes,  annelids,  molluscs  and 
crustaceans ;  Bclostoina  sometimes  pierces  the  bodies  of  tad- 
poles and  small  fishes ;  Dytiscus  also  kills  young  fishes  occa- 
sionally and  is  distinctly  carnivorous  both  as  larva  and  imago. 
Among  terrestrial  insects,  Carabid?e  are  notably  predaceous, 
preying  not  only  upon  other  insects  but  also  upon  molluscs, 
myriopods,  mites  and  spiders.  Ants  do  not  hesitate  to  attack  all 
kinds  of  animals;  in  the  tropics,  the  wandering  ants  (Eciton) 
attack  lizards,  rats  and  other  vertebrates,  and  it  is  said  that 
even  huge  serpents,  when  in  a  torpid  condition,  are  sometimes 
killed  by  armies  of  these  pugnacious  insects. 

]\Iosquitoes  affect  not  only  mammals  but  also,  though 
rarely,  fishes  and  turtles.  The  gad  flies  (Tabanidse)  torment 
horses  and  cattle  by  their  punctures;  and  the  black-flies,  or 
buffalo  gnats  (Siimtliuni) ,  persecute  horses,  mules,  cattle, 
fowls,  and  frequently  become  unendurable  even  to  man.  The 
notorious  tsetse  fly  {Glossiiia  morsifaiis)  of  South  Africa 
spreads  a  deadly  disease  among  horses,  cattle  and  dogs,  by 

276 


INSECTS    IN    RELATION    TO    OTHER    ANIMALS  2/7 

inocnlafing  them  with  a  protozoan  l)loo(l-parasite,  to  the  effects 
of  whicli.  fortunately,  man  is  not  susceptihle. 

Parasitic  Insects. — Insects  l)cl()no-ing-  to  several  diverse 
orders  have  hecomc  ])ccnliarl}-  modified  to  exist  as  parasites 
either  upon  or  within  the  hodies  of  birds  or  mammals. 

Almost  all  birds  are  infested  by  Mallophaga,  or  Ijird  lice,  of 
which  Kellogg  has  catalogued  264  species  from  257  species  of 
Xorth  American  birds.  Sometimes  a  species  of  Mallophaga  is 
restricted  to  a  single  species  of  bird,  though  in  the  majority  of 
cases  this  is  not  so.  Several  mallophagan  species  often  infest 
a  single  bird;  thus  nine  species  occur  on  the  hen,  and  no  less 
than  twelve  species,  representing  five  genera,  on  the  American 
coot.  These  parasites  spread  by  contact  from  male  to  female, 
from  old  to  young,  and  from  one  bird  to  another  when  the 
birds  are  gregarious.  Wdien  a  single  species  of  bird  louse 
occurs  on  two  or  more  hosts,  these  are  almost  always  closely 
allied,  and  Kellogg  has  suggested  the  interesting  possibility 
that  such  a  species  has  persisted  unchanged  from  a  host  which 
was  the  common  ancestor  of  the  two  or  more  present  hosts. 
^Mallophaga  are  not  altogether  limited  to  birds,  however,  for 
they  may  be  found  on  cattle,  horses,  cats,  dogs,  and  some  other 
mammals ;  Kellogg  records  eighteen  species  from  fifteen 
species  of  mammals.  These  biting  lice  feed,  not  upon  blood, 
l)ut  upon  epidermal  cells  and  portions  of  feathers  or  hairs. 
They  have  flat  tough  bodies  (Fig.  17),  with  no  traces  of  wings, 
and  a  large  head  with  only  simple  eyes ;  the  eggs  are  glued  to 
feathers  or  hairs. 

iNIammals  only  are  infested  by  the  sucking  lice,  or  Pediculidce 
(Hemiptera).  These  (Fig.  2t,)  have  a  large  oval  or  rounded 
abdomen,  no  wings,  a  small  head,  minute  simple  eyes  or  none, 
and  claws  that  are  adapted  to  clutch  hairs ;  the  eggs  are  glued 
to  hairs.  Sucking  lice  affect  horses,  cattle,  sheep,  dogs,  mon- 
keys, seals,  elephants,  etc.,  and  man  is  parasitized  by  three 
species,  namely,  the  head  louse  (Pcdiciiliis  caj^itis),  the  body 
louse  {Pcdiciiliis  I'csfiiiiciifi) ,  and  the  crab  louse  (Phthirius 
pubis),  though  the  first  two  are  possibly  the  same  species. 


278  ENTOMOLOGY 

An  anomalous  beetle,  PlatypsyUiis  casforis,  occurs  through- 
out North  America  and  also  in  Europe  as  a  parasite  of  the 
beaver. 

The  fleas,  allied  to  Dii:)tera  but  constituting  a  distinct  order 
( Siphonaptera),  are  familiar  parasites  of  chickens,  cats,  dogs 
and  human  beings.  These  insects  (Fig.  30)  are  well  adapted 
by  their  laterally  compressed  bodies  for  slipping  about  among 
hairs,  and  their  saltatory  powers  and  general  elusiveness  are 
well  known.  Their  wings  are  reduced  to  mere  rudiments,  their 
eyes  when  present  are  minute  and  simple  and  their  mouth 
parts  are  suctorial. 

Among  Diptera,  there  are  a  few  external  parasites,  the  best 
known  of  which  is  the  sheep  tick  {Mdophagiis  0T'/;/;/,y) ,  though 
several  highly  interesting  but  little-studied  forms  are  parasitic 
upon  birds. and  bats. 

The  larvse  of  the  hot  flies  (CEstridcX)  are  common  internal 
parasites  of  mammals.  The  sheep  hot  fly  {CEsfnis  oi'is) 
deposits  her  eggs  or  lar\'?e  on  the  nostrils  of  sheep:  the 
maggots  develop  in  the  frontal  sinuses  of  the  host,  causing 
vertigo  or  even  death,  and  when  full  grown  escape  through 
the  nostrils  and  pupate  in  the  soil.  The  horse  bot  fly  {Gas- 
trophilus  eqiii)  glues  its  eggs  to  the  hairs  of  horses,  especially 
on  the  fore  legs  and  shoulders,  whence  the  larvce  are  licked  off 
and  swallowed;  once  in  the  stomach,  the  hots  fasten  them- 
selves to  its  lining,  1)y  means  of  special  hooks,  and  withstand 
almost  all  eft'orts  to  dislodge  them ;  though  when  the  hots  have 
attained  their  growth  they  release  their  hold  and  pass  with  the 
excrement  to  the  soil.  Bots  of  the  genus  Hypodcnua  form 
tumors  on  cattle  and  other  mammals,  domesticated  or  wild. 
The  ox-warble  (H.  lincata,  Fig.  210,  /)  reaches  the  oesophagus 
of  its  host  in  the  same  manner  as  the  horse  bot,  according  to 
Curtice,  but  then  makes  its  way  into  the  subcutaneous  tissue 
and  causes  the  well-known  tumors  on  the  back  of  the  animal; 
when  full  grown  the  bots  squirm  out  of  these  tumors  and  drop 
to  the  ground,  leaving  permanent  holes  in  the  hide. 

Parasitism  in  General. — Parasitic  insects  evidentlv  do  not 


INSECTS    IN    RELATION    TO    OTHER    AXniALS  2/9 

constitute  a  phylog-cnetic  unit,  Imt  the  parasitic  habit  has  arisen 
independently  in  many  different  orders.  These  insects  do. 
however,  agree  superficially,  in  certain  respects,  as  the  result 
of  what  may  be  termed  convergence  of  adaptation.  Thus  a 
dipterous  larx'a,  li\-ing  as  an  internal  ])arasite.  in  the  i)resence 
of  an  abundant  supply  of  food,  has  no  legs,  no  e}"es  or  anten- 
nae, and  the  head  is  reduced  to  a  mere  rudiment,  sufticient 
simply  to  support  a  pair  of  feeble  jaws;  the  skin,  moreover,  is 
no  longer  armor-like  l)ut  is  thin  and  delicate,  the  body  is  com- 
pact and  fleshy,  and  the  digestive  system  is  of  a  simplified  type. 
The  same  modilications  are  found  in  hymenopterous  larv?e, 
under  similar  food-conditions,  except  that  the  head  usually 
undergoes  less  reduction.  The  various  external  parasites  lack 
wings,  almost  invariably,  and  the  eyes,  instead  of  being  com- 
pound, are  either  simple  or  else  absent.  In  some  special  cases, 
however,  as  in  a  few  dipterous  parasites  of  birds  and  bats,  the 
wings  are  present,  either  permanently  or  only  temporarily, 
enabling  the  insects  to  reach  their  hosts. 

This  so-called  parasitic  degeneration,  widespread  among 
animals  in  general  and  consisting  chiefly  in  the  reduction  or 
loss  of  locomotor  and  sensory  functions  in  correlation  with  an 
immediate  and  plentiful  supply  of  food,  results  in  a  simplicity 
of  organization  which  is  to  be  regarded — not  as  a  primitive 
condition — but  as  an  expression  of  what  is,  in  one  sense,  a 
high  degree  of  specialization  to  peculiar  conditions  of  life. 
This  exquisite  degree  of  adaptation  to  a  special  environment, 
however,  sacrifices  the  general  adaptability  of  the  animal, — 
makes  it  impossible  for  a  parasite  to  adapt  itself  to  new  con- 
ditions ;  and  while  parasitism  may  be  an  immediate  advantage 
to  a  species,  there  are  few  parasites  that  have  attained  any 
degree  of  dominance  among  animals.  Ichneumonidce,  to  be 
sure,  are  remarkably  dominant  among  insects,  but  here  the 
parasitic  adaptations  are  limited  for  the  most  part  to  the  larval 
stage  and  the  adults  may  be  said  to  be  as  free  for  new  adapta- 
tions as  are  any  other  Hymenoptera. 

Scavenger  and  Carrion  Insects. — Not  a  few  families  of 


28o  ENTOMOLOGY 

Diptera  and  Coleoptera  derive  their  food  from  dead  animal 
matter.  The  aquatic  famihes  Dytiscid?e  and  Gyrinidse  are 
largely  scavengers.  Among  terrestrial  forms,  Silphidse  feed 
on  dead  animals  of  all  kinds;  the  burying  beetles  (Necroph- 
onts).  working  in  pairs,  undermine  and  bury  the  bodies  of 
birds,  frogs  and  other  small  animals,  and  lay  their  eggs  in  the 
carcasses ;  Histerid?e  and  Staphylinicke  are  carrion  beetles,  and 
Dermestid^  attack  dried  animal  matter  of  almost  every  de- 
scription, their  depredations  upon  furs,  feathers,  museum 
specimens,  etc.,  being  familiar  to  all.  Ants  are  famous  as 
scavengers,  destroying  decaying  organic  matter  in  immense 
quantities,  particularly  in  the  tropics.  ]\Iany  Scarab^eidse  feed 
upon  excrementitious  matter,  for  example  the  "  tumble-bugs," 
which  are  frequently  seen  in  pairs,  laboriously  rolling  along  or 
burying  a  large  ball  of  dung,  which  is  to  serve  as  food  for  the 
larva. 

Insects  as  Food  for  Vertebrates. — Lizards,  frogs  and 
toads  are  insectivorous,  especially  toads.  The  American  toad 
feeds  chiefly  upon  insects,  which  form  yy  per  cent,  of  its  food 
for  the  season,  the  remainder  consisting  of  myriopods,  spiders, 
Crustacea,  molluscs  and  worms,  according  to  the  observations 
of  A.  H.  Kirkland,  who  states  that  Lepidoptera  form  28  per 
cent,  of  the  total  insect  food,  Coleoptera  27,  Hymenoptera  19 
and  Orthoptera  3  per  cent.  The  toad  does  not  capture  dead 
or  motionless  insects  but  uses  its  extensile  sticky  tongue  to  lick 
in  moving  insects  or  other  prey,  which  it  captures  with  sur- 
prising speed  and  precision.  In  the  cities  one  often  sees  many 
toads  under  an  arc-light  engaged  in  catching  insects  that  fall 
anywhere  near  them.  Though  its  diet  is  varied  and  some- 
what indiscriminate,  the  toad  consumes  such  a  large  propor- 
tion of  noxious  insects,  such  as  May  beetles  and  cutworms, 
that  it  is  unquestionably  of  service  to  man. 

Aloles  are  entirely  insectivorous  and  destroy  large  numbers 
of  white  grubs  and  caterpillars ;  field  mice  and  prairie  squirrels 
eat  many  insects,  especially  grasshoppers,  and  the  skunk  rev- 
els in  these  insects,  though  it  eats  beetles  frequently,  as  does 


INSECTS    IN    RELATION    TO    OTHER    ANIMALS  28 1 

also  the  raccoon,  whicli  is  to  some  extent  insectivorous. 
Monkeys  are  onini\-orotis  l)nt  dcNonr  many  kinds  of  insects. 

W'itli  these  hasty  references,  we  may  i)ass  at  once  to  tlie 
siil)ject  of  the  insect  food  of  hshes  and  l)irds. 

Insects  in  Relation  to  Fishes. — Insects  constitute  the 
most  important  portion  of  the  food  of  a(hdt  fresh  water  fishes, 
furnishiui^-  forty  per  cent,  of  their  food,  acconhng-  to  Dr. 
Forhes,  from  whose  vahia1)le  writint^s  the  followint^-  extracts 
are  taken, 

"  The  principal  insecti\'orous  tishes  are  the  smaller  species, 
whose  size  and  food  structures,  when  adult,  unht  them  for  the 
capture  of  Entomostraca,  and  yet  do  not  bring-  them  within 
reach  of  fishes  or  Mollusca.  Some  of  these  fishes  have  pecu- 
liar habits  which  render  them  especially  dependent  upon  insect 
life,  the  little  minnow  Phciiacobiiis,  for  example,  which,  ac- 
cording to  my  studies,  makes  nearly  all  its  food  from  insects 
( ninety-eight  per  cent. )  found  under  stones  in  running  water. 
Xext  are  the  pirate  perch,  Aplivcdodcnis  (ninety-one  per 
cent. ) ,  then  the  darters  ( eighty-seven  per  cent. ) ,  the  croppies 
(seventy-three  per  cent.),  half-grown  sheepshead  (seventy- 
one  per  cent.),  the  shovel  fish  (fifty-nine  per  cent.),  the  chub 
minnow  (fifty-six  per  cent.) ,  the  black  warrior  sunfish  (CIktiio- 
bryttus)  and  the  brook  silversides  (each  fifty-four  per  cent.), 
and  the  rock  bass  and  the  cyprinoid  genus  Notropis  (each 
fifty-two  per  cent.). 

"  Those  which  take  few  insects  or  none  are  mostly  the  mud- 
feeders  and  the  ichthyophagous  species,  Ainia  (the  dog-fish) 
being  the  only  exception  noted  to  this  general  statement. 
Thus  we  find  insects  wholly  or  nearly  absent  from  the  adult 
dietary  of  the  burbot,  the  pike,  the  gar,  the  black  bass,  the  wall- 
eyed pike,  and  the  great  river  catfish,  and  from  that  of  the 
hickory  shad  and  the  mud-eating  minnows  (the  shiner,  the  fat- 
head, etc.).  It  is  to  be  noted,  however,  that  the  larger  fishes 
all  go  through  an  insectivorous  stage,  whether  their  food 
when  adult  be  almost  wholly  other  fishes,  as  with  the  gar  and 
the   pike,   or   molluscs,   as   with   the   sheepshead.     The   mud- 


282  ENTOMOLOGY 

feeders,  however,  seem  not  to  pass  through  this  stage,  but  to 
adopt  the  Hmophagous  habit  as  soon  as  they  cease  to  depend 
upon  Entomostraca. 

"  Terrestrial  insects,  dropping  into  the  water  accidentally 
or  swept  in  l)y  rains,  are  evidently  diligently  sought  and 
largeh-  depended  upon  by  several  species,  such  as  the  pirate 
perch,  the  brook  minnow,  the  top  minnows  or  killifishes 
( cyprinodonts ) ,  the  toothed  herring  and  several  cyprinoids 
{Scnwtiliis,  Piuicphalcs  and  Notropis). 

"  Among  aquatic  insects,  minute  slender  dipterous  larvae, 
belonging  mostly  to  Chironoinus,  Corcthra  and  allied  genera, 
are  of  remarkable  importance,  making,  in  fact,  nearly  one 
tenth  of  the  food  of  all  the  fishes  studied.  They  are  most 
abundant  in  Pliciiacobius  and  Ethcostoiiia,  which  genera  have 
become  especially  adapted  to  the  search  for  these  insect  forms 
in  shallow  rocky  streams.  Next  I  found  them  most  generally 
in  the  jiirate  perch,  the  brook  silversides,  and  the  stickleback, 
in  which  they  averaged  forty-five  per  cent.  They  amounted 
to  about  one  third  the  food  of  fishes  as  large  and  important 
as  the  red  horse  and  the  river  carp,  and  made  nearly  one  fourth 
that  of  fifty-one  buffalo  fishes.  They  appear  further  in  con- 
siderable quantity  in  the  food  of  a  number  of  the  minnow 
family  (Notropis,  Pimcphalcs.  etc.),  which  habitually  fre- 
quent the  swift  waters  of  stony  streams,  but  were  curiously 
deficient  in  the  small  collection  of  miller's  thumbs  (Cottid?e) 
which  hunt  for  food  in  similar  situations.  The  sunfishes  eat 
but  few  of  this  important  group,  the  average  of  the  famil) 
being  only  six  per  cent. 

"  Larvns  of  aquatic  beetles,  notwithstanding  the  abundance 
of  some  of  the  forms,  occurred  in  only  insignificant  ratios,  but 
were  taken  by  fifty-six  specimens,  belonging  to  nineteen  of  the 
species, — more  frequently  by  the  sunfishes  than  by  any  other 
group.  The  kinds  most  commonly  captured  were  larvae  of 
Gyrinidae  and  Hydrophilidae ;  whereas  the  adult  surface  beetle? 
themselves  {Gyrinus,  Dincutcs,  etc.) — whose  zigzag-darting 
swarms  no  one  can  have  failed  to  notice — were  not  once  en- 
countered in  my  studies. 


TNSECTS    IN    RELATION    TO    OTHER    ANIMALS  283 

"  The  almost  equally  well-known  slender  water-skippers 
{H\i^iu>trrcJius)  seem  also  C(Mn])letely  ]:)r()tectc(l  by  their  habits 
and  acti\-it\'  from  capture  b_\'  tishcs,  only  a  singie  specimen  oc- 
curring in  the  food  of  all  my  s])ecimens.  Indeed,  the  true 
water  bugs  (  llemiptera)  were  generally  rare,  with  the  excep- 
tion of  the  small  soft-bodied  genus  Corisa,  which  was  taken  by 
one  hundred  and  ten  specimens,  belonging  to  twenty-seven 
species, — most  alnindantly  by  the  sunfishes  and  top  minnows. 

"  h'rom  the  order  Neuroptera  [in  the  broad  sense]  fishes 
draw  a  larger  part  of  their  food  than  from  any  other  single 
group.  In  fact,  nearly  a  hfth  of  the  entire  amount  of  food 
consumed  by  all  the  adult  hshes  examined  b}'  me  consisted  of 
aquatic  larvce  of  this  order,  the  greater  part  of  them  larvae  of 
day  flies  (Ephemerid?e),  principally  of  the  genus  Hcxagenia. 
These  neuropterous  larvse  were  eaten  especially  by  the  miller's 
thumb,  the  sheepshead,  the  white  and  striped  bass,  the  common 
perch,  thirteen  species  of  the  darters,  both  the  black  bass,  seven 
of  the  sunfishes,  the  rock  bass  and  the  croppies,  the  pirate 
perch,  the  brook  silversides,  the  sticklebacks,  the  mud  minnow, 
the  top  minnows,  the  gizzard  shad,  the  toothed  herring,  twelve 
species  each  of  the  true  minnow  family  and  of  the  suckers  and 
buffalo,  li\e  catfishes,  the  dog-fish,  and  the  shovel  fish, — 
seventy  species  out  of  the  eighty-seven  which  I  ha\'e  studied. 

"  Among  the  above,  I  found  them  the  most  important  food 
of  the  white  bass,  the  toothed  herring,  the  shovel  fish  (fifty- 
t)ne  per  cent.),  and  the  croppies;  while  they  made  a  fourth  or 
more  of  the  alimentary  contents  of  the  sheepshead  ( forty-six 
per  cent.),  the  darters,  the  pirate  perch,  the  common  sunfishes 
{Lcpoinis  and  CJiccnohrytius) .  the  rock  l^ass,  the  little  pickerel, 
and  the  common  sucker  (thirty-six  per  cent.). 

"  Ephemerid  larvcC  were  eaten  by  two  hundred  and  thirteen 
specimens  of  forty-eight  species — not  counting  young.  The 
larvcT  of  Hcxagenia,  one  of  the  commonest  of  the  '  river 
flies,'  was  by  far  the  most  important  insect  of  this  group,  this 
alone  amounting  to  about  half  of  all  the  Neuroptera  eaten. 
Thev  made  nearlv  one  half  of  the  food  of  the  shovel  fish,  more 


284  ENTOMOLOGY 

than  one  tenth  that  of  the  sunfishes,  and  the  principal  food  re- 
sources of  half-grown  sheepshead ;  but  were  rarely  taken  by 
the  sucker  family,  and  made  only  five  per  cent,  of  the  food  of 
the  catfish  group. 

"  The  various  larvae  of  the  dragon  flies,  on  the  other  hand, 
were  much  less  frequently  encountered.  They  seemed  to  be 
most  a1)undant  in  the  food  of  the  grass  pickerel  (twenty-five 
per  cent.),  and  next  to  that,  in  the  croppie.  the  pirate  perch, 
and  the  common  perch  (ten  to  thirteen  per  cent.). 

"  Case-worms  (Phryganeidse)  were  somewhat  rarely 
found,  rising  to  fifteen  per  cent,  in  the  rock  bass  and  tweh'e 
per  cent,  in  the  minnows  of  the  Hybopsis  group,  but  otherwise 
averaging  from  one  to  six  per  cent,  in  less  than  half  of  the 
species." 

Insects  in  Relation  to  Birds. — From  an  economic  point 
of  view  the  relations  between  birds  and  insects  are  extremely 
important,  and  from  a  purely  scientific  standpoint  they  are  no 
less  important,  involving  as  they  do  biological  interactions  of 
remarkable  complexity. 

The  prevalent  popular  opinion  that  birds  in  general  are  of 
inestimable  value  as  destroyers  of  noxious  insects  is  a  correct 
one,  as  Dr.  Forbes  proved,  from  his  precise  and  extensive 
studies  upon  the  food  of  Illinois  birds,  involving  a  laborious 
and  difficult  examination  of  the  stomach  contents  of  many 
hundred  specimens.  All  that  follows  is  taken  from  Forbes, 
when  no  other  author's  name  is  mentioned,  and  though  the 
percentages  given  by  Forbes  apply  to  particular  years  and 
would  undoubtedly  vary  more  or  less  from  year  to  year,  they 
are  here  for  convenience  regarded  as  representative  of  any 
year  and  are  spoken  of  in  the  present  tense.  About  two  thirds 
of  the  food  of  birds  consists  of  insects. 

Robin. — The  food  of  the  robin  in  Illinois,  from  February  to 
Alay  inclusive,  consists  almost  entirely  of  insects ;  at  first, 
larvae  of  Bibio  albipciiiiis  for  the  most  part,  and  then  caterpil- 
lars and  various  beetles.  When  the  small  fruits  appear,  these 
are  largely  eaten  instead  of  insects ;  thus  in  June,  cherries  and 


INSECTS    IN    RELATION    TO    OTHER    ANIMALS  285 

raspberries  form  fifty-li\e  ])er  cent,  and  insects  (ants,  cater- 
pillars, \vire-\V(»rms  and  l"aral)id;c)  forty-two  ])er  cent,  of  tlie 
food :  and  in  Jnly,  ras])l)erries.  blackberries  and  currants  form 
seventv-nine  per  cent,  and  insects  (mostly  caterpillars,  beetles 
and  crickets)  l)nt  twenty  per  cent,  of  the  food.  In  Angnst. 
insects  rise  to  forty-three  per  cent,  and  fruits  drop  to  tifty-six 
per  cent.,  and  these  are  mostly  cherries,  of  which  two  thirds 
are  wild  kinds.  In  Septemljer.  ants  form  tifteen  per  cent,  of 
the  food,  caterpillars  five  per  cent,  and  fruits  (mostly  grapes, 
mountain-ash  berries  and  moonseed  berries)  seventy  per  cent. 
In  October,  the  food  consists  chiefly  of  wild  grapes  (fifty- 
three  per  cent.),  ants  (thirty-five  per  cent.),  and  caterpillars 
(six  per  cent.). 

For  the  }-ear,  judging  from  the  stomach  contents  of  one 
hundred  and  fourteen  birds,  garden  fruits  form  only  tw^enty- 
nine  per  cent,  of  the  food  of  the  robin,  while  insects  constitute 
two  thirds  of  the  food.  The  results  are  confirmed  by  those 
of  Professor  Beal  in  Michigan,  who  found  that  more  than 
forty-two  per  cent,  of  the  food  of  the  robin  consists  of  insects 
with  some  other  animal  matter,  the  remainder  being  made  up 
of  \arious  small  fruits,  but  notably  the  wild  kinds. 

Upon  the  whole,  the  robin  deserves  to  be  protected  as  an 
energetic  destroyer  of  cutworms,  wdiite  grubs  and  other  injuri- 
ous insects,  and  the  comparatively  few  culti\-ated  berries  that 
the  bird  appropriates  are  ordinarily  but  a  meagre  compensa- 
tion for  the  valuable  ser\-ices  rendered  to  man  by  this  familiar 
bird. 

Catbird. — Xot  so  much  can  be  said  for  the  catbird,  however, 
for  though  its  food  habits  are  similar  to  those  of  the  robin,  it 
arrives  later  and  departs  earlier,  with  the  result  that  it  is  less 
dependent  than  the  robin  upon  insects  and  that  berries  form  a 
larger  percentage  of  its  total  food. 

In  May,  eighty-three  per  cent,  of  the  food  of  the  catbird 
consists  of  insects,  mostly  beetles  (Carabidje,  Rhynchophora, 
etc.),  crane-flies,  ants  and  caterpillars  (Noctuidae)  ;  while  dry 
sumach  berries  are  eaten  to  the  extent  of  seven  per  cent.     For 


286  ENTOMOLOGY 

the  first  half  of  June,  the  record  is  much  the  same,  with  an  in- 
crease, ho\ve\er,  in  the  num1)er  of  May  beetles  eaten ;  in  the 
second  half  of  the  month,  the  food  consists  chiefly  of  small 
fruits,  especially  raspberries,  cherries  and  currants ;  so  that  for 
the  month  as  a  whole,  only  forty-nine  per  cent,  of  the  food  is 
made  up  of  insects.  This  falls  to  eighteen  per  cent,  in  July, 
when  three  quarters  of  the  food  consists  of  small  fruits, 
mostly  blackberries,  however.  In  August,  with  the  diminu- 
tion of  the  smaller  cultivated  fruits,  the  percentage  of  insects 
rises  to  forty-six  per  cent.,  nearly  one  half  of  which  is  made 
up  of  ants  and  the  rest  of  caterpillars,  grasshoppers,  Hemip- 
tera,  Coleoptera,  etc.  In  September,  with  the  appearance  of 
wild  cherries,  elderberries,  Virginia  creeper  berries  and 
grapes,  these  are  eaten  to  the  extent  of  seventy-six  per  cent., 
the  insect  element  of  the  food  falling  to  twenty-one  per  cent., 
of  which  almost  half  consists  of  ants,  and  the  remainder  of 
beetles  and  a  few  caterpillars. 

For  the  entire  year,  as  appears  from  the  study  of  seventy 
specimens  by  Forbes,  insects  form  forty-three  per  cent,  of  the 
food  of  the  catbird  and  fruits  fifty-two  per  cent.  As  the  in- 
jurious insects  killed  are  ofTset  by  the  beneficial  ones  destroyed, 
"  the  injury  done  in  the  fruit-garden  by  these  birds  remains 
without  compensation  unless  we  shall  find  it  in  the  food  of  the 
voung,"  says  Professor  Forbes.  And  this  has  been  found,  to 
the  credit  of  the  catbird ;  for  Weed  learned  that  the  food  of 
three  nestlings  consisted  of  insects,  sixty-two  per  cent,  of 
which  were  cutworms  and  four  per  cent,  grasshoppers ;  while 
Judd  found  that  fourteen  nestlings  had  eaten  but  four  per 
cent,  of  fruit,  the  diet  being  chiefly  ants,  beetles,  caterpillars, 
spiders  and  grasshoppers.  In  fact.  Weed  believes  that,  on 
the  whole,  the  benefit  received  from  the  catbird  is  much  greater 
than  the  harm  done,  and  that  its  destruction  should  never  be 
permitted  except  when  necessary  in  order  to  save  precious 
crops. 

Bluebird. — The  excellent  reputation  which  the  bluebird 
bears  everywhere  as  an  enemy  of  noxious  insects  is  well-de- 


INSECTS    IN    RELATION    TO    OTHER    ANIMAES  28/ 

served.  Fiv^m  a  stndv  (if  one  hundred  and  ei,<;ht  illinois  si~)cci- 
mens,  h^)rl)es  finds  lliat  se\'enty-eit;'lil  per  cent,  of  tlie  food  for 
tlie  year  consists  of  insects,  eight  per  cent,  of  .\rachnida,  one 
per  cent,  of  jnhd;e  and  only  thirteen  per  cent,  of  veo-eta1)le 
matter.  e(hble  fruits  forming  merely  one  per  cent,  of  the  entire 
food.  The  insects  eaten  are  mostl}-  cater])illars  (chielly  cut- 
worms). Orthoptera  (grasshoppers  and  crickets)  and  Cole- 
ojitera  (Carabichc  and  Scaral)<Ti(l;e ).  ddiough  some  of  the 
insects  are  more  or  less  beneficial  to  man.  such  as  C'arabid.-e 
and  IchneumonidcT  (respectively  predaceous  and  parasitic), 
the  beneficial  elements  form  only  twenty-two  per  cent,  of  the 
food  for  the  vear.  as  against  forty-nine  per  cent,  of  injurious 
elements,  the  remaining  twenty-nine  per  cent,  consisting  of 
neutral  elements.  The  food  of  the  nestlings,  according  to 
Judd.  is  essentially  like  that  of  the  adults,  being  "  Ijeetles. 
caterpillars,  grasshoppers,  spiders  antl  a  few  snails." 

Other  Insectivorous  Birds. — Weed  and  Dearborn,  from 
whose  excellent  work  the  following  notes  are  taken,  find  that 
the  common  chickadee  devours  immense  numbers  of  canker- 
worms,  and  that  more  than  half  its  food  during  winter  con- 
sists of  insects,  largely  in  the  form  of  eggs,  including  those  of 
the  common  tent  caterpillar  ( C.  aincricaiia)  <  the  fall  web- 
worm  {H.  ciiiica)  and  particularly  plant  lice,  whose  eggs, 
small  as  they  are.  form  more  than  one  fifth  of  the  entire  food; 
more  than  four  hundred  and  fifty  of  them  are  sometimes  eaten 
by  a  single  bird  in  one  day.  and  the  total  number  destroyed 
annually  is  inconceivably  large.  The  house  wren  is  alm;)st 
exclusively  insectivorous,  feeding  upon  caterpillars  and  other 
larvae,  ants,  grasshoppers,  gnats,  beetles,  bugs,  spiders,  and 
myriopods.  The  swallows,  also,  are  highly  insectivorous; 
"  most  of  their  food  is  captured  on  the  wing",  and  consists  of 
small  moths,  two-winged  flies,  especially  crane-flies,  beetles  in 
great  variety,  flying-  bugs,  and  occasionally  small  dragon-flies. 
The  young  are  fed  with  insects."  Ninety  per  cent,  of  the  food 
of  the  kingbird  "  consists  of  insects,  including  such  noxious 
species  as  May-beetles,  click-beetles,  wheat  and  fruit  weevils. 


288 


ENTOMOLOGY 


grasshoppers,  and  leafhoppers."  The  honey  bees  eaten  l)y 
this  bird  are  insignificant  in  number.  \\^oodpeckers  destroy 
immense  numbers  of  wood-boring  larvae,  bark-insects,  ants, 
caterpillars,  etc.  The  cuckoos  "  are  unique  in  having  a  taste 
for  insects  that  other  birds  reject.  Most  birds  are  ready  to 
devour  a  smooth  caterpillar  that  comes  in  their  way,  but  they 
leave  the  hairy  varieties  severely  alone.  The  cuckoos,  how- 
ever, make  a  specialty  of  devouring  such  unpalatable  crea- 
tures :  e\en  stink-bugs  and  the  poisonous  spiny  larv?e  of  the  lo 
moth  are  freely  taken."  Caterpillars  form  fifty  per  cent,  of 
the  food  for  the  year;  Orthoptera  (grasshoppers,  katydids, 
and  tree  crickets),  thirty  per  cent. ;  Coleoptera  and  Hemiptera, 
six  per  cent,  each ;  and  flies  and  ants  are  taken  in  small  quanti- 
ties. "  The  nestling  birds  are  fed  chiefly  with  smooth  cater- 
pillars and  grasshoppers,  their  stomachs  probably  being  unable 
to  endure  the  hairy  caterpillars.  All  in  all.  the  cuckoos  are  of 
the  highest  economic  value.  They  do  no  harm  and  accom- 
plish great  good.  If  the  orchardist  could  colonize  his  or- 
chards with  them,  he  would  escape  much  loss."  The  quail 
feeds  largely  upon  insects  during  the  summer,  frequently  eat- 
ing the  Colorado  potato  beetle  and  the  army  worm ;  the  prairie 
hen  has  similar  food  habits  but  lives  almost  exclusively  on 
grasshoppers,  when  these  are  abundant. 

The  Insect  Food  of  Birds. — "  There  are  few  groups  of 
injurious  insects  that  enter  so  largely  into  the  composition  of 
the  food  of  birds  as  do  the  locusts,  or  short-horned  grasshop- 
pers, of  the  family  Acridiid^e.  The  enormous  destructive 
power  of  these  insects  is  well  known,  but  our  indebtedness  to 
birds  in  checking  their  oscillations  is  less  generally  recog- 
nized." Professor  Aughey.  who  has  made  extensive  studies 
upon  the  relation  of  birds  to  the  Rocky  Mountain  locust, 
found  that  upon  one  occasion  6  robins  had  eaten  265  of  these 
insects,  5  catbirds  152.  3  bluebirds  67.  7  barn  swallows  139,  7 
night  hawks  348.  16  yellow-billed  cuckoos  416,  8  flickers  252. 
8  screech  owls  219.  and  i  humming  bird  4;  while  crows  and 
blue-jays  had  eaten  large  numbers  of  the  locusts ;  and  grouse. 


INSECTS    IN    RELATION    TO    OTHER    ANIMALS  289 

quail  and  prairie  hen,  enormons  numbers.  Even  shore  birds, 
such  as  g-eese,  ducks,  guhs  and  pehcans  came  to  share  in  the 
feast.  Aughey  estimated  that  the  locusts  eaten  in  one  day  by 
the  passerine  birds  of  the  eastern  half  of  Nebraska  were 
sufficient  to  destroy  in  a  single  day  174.397  tons  of  crops, 
valued  at  $1,743.97. 

Weed  and  Dearborn  state  that,  of  Hemiptera,  Jassidse  are  very 
often  found  in  the  stomachs  of  birds,  and  that  aphids  and  their 
eggs  form  a  large  part  of  the  food  of  many  of  the  smaller  birds, 
such  as  the  warblers,  nuthatches,  kinglets  and  chickadees. 
"  A  large  proportion  of  the  caterpillars  of  the  Lepidoptera  are 
eagerly  devoured  by  birds,  forming"  an  important  element  of 
the  food  of  many  species."  The  hairy  caterpillars  are  eaten 
by  cuckoos  and  blue-jays  and  the  large  saturniid  caterpillars, 
such  as  cecropia  and  polypJiemus,  by  some  of  the  hawks.  Al- 
most all  kinds  of  Coleoptera  are  food  for  birds,  but  especially 
the  grubs  of  Scarabceidse,  which  are  eagerly  devoured  by 
robins,  blackbirds,  crows  and  other  birds.  Of  the  Diptera, 
Cecidomyiidae  and  other  gnats  are  eaten  by  swallows,  swifts 
and  night  hawks ;  while  Tipulidae  are  often  found  in  the  stom- 
achs of  birds.  Among  Hymenoptera,  ants  are  eaten  exten- 
sively by  woodpeckers,  catbirds  and  many  other  species,  as  are 
also  Ichneumonida^  and  other  parasitic  forms — these  last  by 
the  flycatchers  in  particular. 

The  Regulative  Action  of  Birds  upon  Insect  Oscilla- 
tions.— The  worst  injuries  by  insects  are  done  by  species  that 
fluctuate  excessively  in  number  as  the  result  of  variations  in 
those  manifold  forces  that  act  as  checks  upon  the  multiplica- 
tion of  the  species. 

In  order  to  determine  whether  birds  do  anything  to  reduce 
existing  oscillations  of  injurious  insects,  Professor  Forbes 
made  some  admirable  studies  upon  the  food  of  birds  which 
were  shot  in  an  Illinois  apple  orchard  which  was  being  ravaged 
by  canker-worms.  In  this  orchard,  birds  were  present  in 
extraordinary  number  and  variety,  there  being  at  least  thirty- 
five   species,   most   of   which   were   studied   by  Forbes,    from 


290  ENTOMOLOGY 

whose  exhaustive  tables  the  following  food-percentages  are 
taken : 

Birds  Examined.        Insects.       Canker-worms. 


Robin, 

9 

93  % 

21 

Catbird, 

14 

98 

15 

Brown  Tlirush, 

4 

94 

12 

Bluebird, 

5 

98 

12 

Black-capped  Chickadee, 

2 

100 

61 

House    Wren, 

5 

91 

46 

Tennessee  Warbler, 

I 

100 

80 

Summer  Yellow  Bird, 

5 

94 

67 

Black-throated  Green  Warbler, 

I 

100 

70 

Maryland  Yellow-throat, 

2 

100 

Zl 

Baltimore   Oriole, 

3 

100 

40 

To  quote  Forbes :  "  Three  facts  stand  out  very  clearly  as 
results  of  these  investigations:  i.  Birds  of  the  most  varied 
character  and  habits,  migrant  and  resident,  of  all  sizes,  from 
the  tiny  wren  to  the  blue-jay,  birds  of  the  forest,  garden  and 
meadow,  those  of  arboreal  and  those  of  terrestrial  habits,  were 
certainly  either  attracted  or  detained  here  by  the  bountiful 
supply  of  insect  food,  and  were  feeding  freely  upon  the  species 
most  abundant.  That  thirty-five  per  cent,  of  the  food  of  all 
the  birds  congregated  in  this  orchard  should  have  consisted  of 
a  single  species  of  insect,  is  a  fact  so  extraordinary  that  its 
meaning  can  not  be  mistaken.  Whatever  power  the  birds  of 
this  vicinity  possessed  as  checks  upon  destructive  irruptions  of 
insect  life,  was  being  largely  exerted  here  to  restore  the  broken 
balance  of  organic  nature.  And  while  looking  for  their  in- 
fluence over  one  insect  outbreak  we  stumbled  upon  at  least  two 
others,  less  marked,  perhaps  incipient,  but  evident  enough  to 
express  themselves  clearly  in  the  changed  food  ratios  of  the 
birds. 

"  2.  The  comparisons  made  show  plainly  that  the  reflex  effect 
of  this  concentration  on  two  or  three  unusually  numerous  in- 
sects was  so  widely  distributed  over  the  ordinary  elements  of 
their  food  that  no  especial  chance  was  given  for  the  rise  of  new 
fluctuations  among  the  species  commonly  eaten.  That  is  to 
say,  the  abnormal  pressure  put  upon  the  canker-worm  and  vine- 


.      INSECTS    IN    RELATION    TO    OTHER    ANIMALS  29 1 

chafer  was  compensated  by  a  general  diminution  of  the  ratios 
of  all  the  other  elements,  and  not  by  a  neglect  of  one  or  two 
alone.  If  the  latter  had  been  the  case,  the  criticism  might 
easily  have  been  made  that  the  birds,  in  helping  to  reduce  one 
oscillation,  were  setting  cithers  on  foot. 

"  3.  The  fact  that,  with  the  exception  of  the  indigo  bird,  the 
species  whose  records  in  the  orchard  were  compared  with  those 
made  elsewhere,  had  eaten  in  the  former  situation  as  many 
caterpillars  other  than  canker-worms  as  usual,  simply  adding 
their  canker-worm  ratios  to  those  of  other  caterpillars,  goes 
to  show  that  these  insects  are  favorites  with  a  majority  of 
birds."' 

The  Relations  of  Birds  to  Predaceous  and  Parasitic  In- 
sects.— The  false  assumption  is  often  made  that  a  bird  is 
necessarily  inimical  to  man's  interest  whenever  it  destroys  a 
parasitic  or  a  predaceous  insect.  Weed  and  Dearborn  attack 
this  assumption  as  follows : 

"  Suppose  an  ichneumon  parasite  is  found  in  the  stomach  of 
a  robin  or  other  bird :  it  may  belong  to  any  one  of  the  follow- 
ing categories : 

"  I.  The  primary  parasite  of  an  injurious  insect. 

"  2.  The  secondary  parasite  of  an  injurious  insect. 

"  3.  The  primary  parasite  of  an  insect  feeding  on  a  noxious 
plant. 

"  4.  The  secondarv  parasite  of  an  insect  feeding  on  a  nox- 
ious plant. 

''  5.  The  primary  parasite  of  an  insect  feeding  on  a  wild 
plant  of  no  economic  value. 

"  6.  The  secondary  parasite  of  an  insect  feeding  on  a  wild 
plant  of  no  economic  value. 

""  7.  The  primary  parasite  of  a  predaceous  insect. 

"  8.  The  primary  parasite  of  a  spider  or  a  spider's  egg. 

"  This  list  might  easily  be  extended  still  farther,  and  the 
assumption  that  the  parasite  belongs  to  the  first  of  these  cate- 
gories is  unwarranted  by  the  facts  and  does  violence  to  the 
probabilities  of  the  case. 


292  ENTOMOLOGY 

"  A  correct  idea  of  the  economic  role  of  the  feathered  tribes 
may  be  obtained  only  by  a  broader  view  of  nature's  methods, 
— a  view  in  which  we  must  ever  keep  before  the  mind's  eye 
the  fact  that  all  the  parts  of  the  organic  world,  from  monad  to 
man,  are  linked  together  in  a  thousand  ways,  the  net  result 
being  that  unstable  equilibrium  commonly  called  '  the  balance 
of  nature.'  " 

This  broader  view  was  first  elaborated  by  Professor  Forbes, 
in  his  masterly  paper,  "  On  Some  Interactions  of  Organisms," 
the  substance  of  wdiich  is  given  below. 

"  Evidently  a  species  can  not  long  maintain  itself  in  num- 
bers greater  than  can  find  sufficient  food,  year  after  year.  If 
it  is  a  phytophagous  insect,  for  example,  it  will  soon  dwindle 
if  it  seriously  lessens  the  numbers  of  the  plants  upon  which  it 
feeds,  either  directly,  by  eating  them  up,  or  indirectly,  by  so 
weakening  them  that  they  labor  under  a  marked  disadvantage 
in  the  struggle  with  other  plants  for  foothold,  air,  light  and 
food.  The  interest  of  the  insect  is  therefore  identical  with 
the  interest  of  the  plant  it  feeds  upon.  Whatever  injuriously 
affects  the  latter,  equally  injures  the  former;  and  whatever 
favors  the  latter,  equally  favors  the  former.  This  must, 
therefore,  be  regarded  as  the  extreme  normal  limit  of  the  num- 
bers of  a  phytophagous  species, — a  limit  such  that  its  depre- 
dations shall  do  no  especial  harm  to  the  plants  upon  which  it 
depends  for  food,  but  shall  remove  only  the  excess  of  foliage 
or  fruit,  or  else  superfluous  individuals  which  must  perish 
otherwise,  if  not  eaten,  or,  surviving,  must  injure  their  species 
by  over-crowding.  If  the  plant-feeder  multiply  beyond  the 
above  limit,  evidently  the  diminution  of  its  food  supply  will 
soon  react  to  diminish  its  own  numbers ;  a  counter  reaction 
will  then  take  place  in  favor  of  the  plant,  and  so  on  through 
an  oscillation  of  indefinite  continuance. 

"  On  the  other  hand,  the  reduction  of  the  phytophagous  in- 
sect below  the  normal  number,  will  evidently  injure  the  food 
plant  by  preventing  a  reduction  of  its  excess  of  growth  or 
numbers,  and  will  also  set  up  an  oscillation  like  the  preceding, 
except  that  the  steps  will  be  taken  in  reverse  order. 


INSECTS    IN    RELATION    TO    OTHER    ANIMALS  293 

"  I  next  point  ont  the  fact  that  precisely  the  same  reasoning 
appHes  to  predaceons  and  parasitic  insects.  Tlieir  interests, 
also  are  identical  with  the  interests  of  the  species  they  para- 
sitize or  prey  upon.  A  diniinntion  of  their  food  reacts  to  de- 
crease their  own  numbers.  The}-  are  thus  vitally  interested 
in  confining-  their  depredations  to  the  excess  of  individuals 
produced,  or  to  redundant  or  otherwise  unessential  structures. 
It  is  only  by  a  sort  of  unlucky  accident  that  a  destructive  spe- 
cies really  injures  the  species  preyed  upon. 

"  The  discussion  has  thus  far  affected  only  such  organisms 
as  are  confined  to  a  single  species.  It  remains  to  see  how  it 
applies  to  such  as  have  several  sources  of  support  open  to 
them, — such,  for  instance,  as  feed  indifferently  upon  several 
plants  or  upon  a  variety  of  animals,  or  both.  Let  us  take, 
first,  the  case  of  a  predaceous  beetle  feeding  upon  a  variety  of 
other  insects. — either  indifferently,  upon  whatever  species  is 
most  numerous  or  most  accessible,  or  preferably  upon  certain 
species,  resorting  to  others  only  in  case  of  an  insufficiency  of 
its  favorite  food. 

"  It  is  at  once  evident  that,  taking  the  group  of  its  food- 
insects  as  a  unit,  the  same  reasoning  applies  as  if  it  were  re- 
stricted to  a  single  species  for  food ;  that  is,  it  is  interested  in 
the  maintenance  of  these  food-species  at  the  highest  number 
consistent  with  the  general  conditions  of  the  environment, — 
interested  to  confine  its  own  depredations  to  that  surplus  of 
its  food  which  would  otherwise  perish  if  not  eaten — interested, 
therefore,  in  establishing  a  rate  of  reproduction  for  itself 
which  will  not  unduly  lessen  its  food  supply.  Its  interest  in 
the  numbers  of  each  species  of  the  group  it  eats  will  evidently 
be  the  same  as  its  interest  in  the  group  as  a  whole,  since 
the  group  as  a  whole  can  be  kept  at  the  highest  number 
possible  only  by  keeping  each  species  at  the  highest  number 
possible.   .   .   . 

"  This  argument  holds  for  birds  as  well  as  for  insects,  for 
animals  of  all  kinds,  in  fact,  whether  their  food  be  mixed  or 
simple,  animal  or  vegetable,  or  both.     It  also  applies  to  para- 


294  ENTOMOLOGY 

sitic  plants.  The  ideal  adjustment  is  one  in  which  the  repro- 
ductive rate  of  each  species  should  be  so  exactly  adapted  to  its 
food  supply  and  to  the  various  drains  upon  it  that  the  species 
preyed  upon  should  normally  produce  an  excess  sufficient  for 
the  species  it  supports.  And  this  statement  evidently  applies 
throughout  the  entire  scale  of  being.  Among  all  orders  of 
plants  and  animals,  the  ideal  balance  of  Nature  is  one  promo- 
tive of  the  highest  good  of  all  the  species.  In  this  ideal  state, 
towards  which  Nature  seems  continually  striving,  every  food- 
producing  species  of  plant  or.  animal  would  grow  and  multiply 
at  a  rate  sufficient  to  furnish  the  required  amount  of  food, 
and  every  depredating  species  w-ould  reproduce  at  a  rate  no 
higher  than  just  sufficient  to  appropriate  the  food  thus  fur- 
nished. .   .   . 

"  Exact  adjustment  is  doubtless  never  reached  anywhere, 
even  for  a  single  year.  It  is  usually  closely  approached  in 
primitive  nature,  but  the  chances  are  practically  infinite  against 
its  becoming  really  complete,  and  mal-adjustment  in  some  de- 
gree is  therefore  the  general  rule.  All  species  must  oscillate 
more  or  less." 

Professor  Forbes  then  shows  that  oscillations  are  injurious 
to  a  species  and  that  the  tendency  of  things  is  toward  a 
healthy  ecjuilibrium.  If  the  rate  of  reproduction,  as  in  a 
parasite  for  instance,  is  too  small  in  relation  to  the  food  sup- 
ply, the  species  will  eventually  yield  to  its  more  prolific  compet- 
itors in  the  general  struggle  for  existence.  If,  on  the  other 
hand,  its  rate  of  multiplication  is  too  high,  the  species  will  be 
at  a  disadvantage  in  the  search  for  food,  as  compared  with 
better  adjusted  species,  and  must  again  suffer.  "  The  fact  of 
survival  is  therefore  usually  sufficient  evidence  of  a  fairly  com- 
plete adjustment  of  the  rate  of  reproduction  to  the  drains  upon 
the  species."  ...  "  We  may  be  sure,  therefore,  that,  as  a 
general  rule,  in  the  course  of  evolution,  only  those  species 
have  been  able  to  survive  whose  parasites,  if  any,  were  not 
prolific  enough  sensibly  to  limit  the  numbers  of  their  hosts  for 
any  length  of  time. 


INSECTS    IN    RELATION    TO    OTHER    ANIMALS  295 

"  We  notice  incidentally  that  it  is  thus  made  unlikely  that  an 
injurious  species  can  be  exterminated,  can  even  be  permanently 
lessened  in  numbers,  by  a  parasite  strictly  dependent  upon  it, — 
a  conclusion  which  remarkably  diminishes  the  economical  role 
of  parasitism.  The  same  line  of  argimient  will,  of  course, 
apply,  with  slight  modifications,  to  any  animal,  or  even  to  any 
plant  dependent  upon  any  other  animal  or  any  other  plant  for 
existence. 

"  It  is  a  general  truth,  that  those  animals  and  plants  are 
least  likely  to  oscillate  widely  which  are  preyed  upon  by  the 
greatest  number  of  species,  of  the  most  varied  habit.  Then 
the  occasional  diminution  of  a  single  enemy  will  not  greatly 
affect  them,  as  any  consequent  excess  of  their  own  numbers 
will  be  largely  cut  down  by  their  other  enemies,  and  especially 
as,  in  most  cases,  the  backward  oscillations  of  one  set  of  ene- 
mies will  be  neutralized  by  the  forward  oscillations  of  another 
set.  But  by  the  operations  of  natural  selection,  most  animals 
are  compelled  to  maintain  a  varied  food  habit, — so  that  if  one 
element  fails,  others  may  be  available.  Thus  each  species 
preyed  upon  is  likely  to  have  a  number  of  enemies,  which  will 
assist  each  other  in  keeping  it  properly  in  check. 

"  Against  the  uprising  of  inordinate  numbers  of  insects, 
commonly  harmless  but  capable  of  becoming  temporarily  in- 
jurious, the  most  valuable  and  reliable  protection  is  un- 
doubtedly afforded  by  those  predaceous  birds  and  insects 
which  eat  a  mixed  food,  so  that  in  the  absence  or  diminution 
of  any  one  element  of  their  food,  their  own  numbers  are  not 
seriously  affected.  Resorting,  then,  to  other  food  supplies, 
they  are  found  ready,  on  occasion,  for  immediate  and  over- 
whelming attack  against  any  threatening  foe.  Especially 
does  the  wonderful  locomotive  power  of  birds,  enabling  them 
to  escape  scarcity  in  one  region  which  might  otherwise  deci- 
mate them,  by  simply  passing  to  another  more  favorable  one, 
without  the  loss  of  a  life,  fit  them,  above  all  other  animals  and 
agencies,  to  arrest  disorder  at  the  start, — to  head  off  aspiring 
and  destructive  rebellion  before  it  has  had  time  fairlv  to  make 


296  ENTOMOLOGY 

head.  But  we  should  not  therefrom  derive  the  general,  but 
false  and  mischievous  notion,  that  the  indefinite  multiplication 
of  either  birds  or  predaceous  insects  is  good.  Too  many  of 
either  is  nearly  or  quite  as  harmful  as  too  few. 

"  There  is  a  general  consent  that  primeval  nature,  as  in  the 
uninhabited  forest  or  the  untilled  plain,  presents  a  settled  har- 
mony of  interaction  among  organic  groups  which  is  in  strong 
contrast  with  the  many  serious  mal-adjustments  of  plants  and 
animals  found  in  countries  occupied  by  man. 

"  To  man,  as  to  nature  at  large,  the  question  of  adjustment 
is  of  vast  importance,  since  the  eminently  destructive  species 
are  the  widely  oscillating  ones.  Those  insects  which  are  well 
adjusted  to  their  environments,  organic  and  inorganic,  are 
either  harmless  or  inflict  but  moderate  injury  (our  ordinary 
crickets  and  grasshoppers  are  examples)  ;  while  those  that  are 
imperfectly  adjusted,  whose  numbers  are,  therefore,  subject 
to  wide  fluctuations,  like  the  Colorado  grasshopper,  the 
chinch-bug  and  the  army  worm,  are  the  enemies  which  we 
have  reason  to  dread.  Man  should  then  especially  address 
his  efforts,  first,  to  prevent  any  unnecessary  disturbance  of  the 
settled  order  of  the  life  of  his  region  which  will  convert  rela- 
tively stationary  species  into  widely  oscillating  ones ;  second, 
to  destroy  or  render  stationary  all  the  oscillating  species  in- 
jurious to  him ;  or,  failing  in  this,  to  restrict  their  oscillations 
within  the  narrowest  limits  possible. 

"  For  example,  remembering  that  every  species  oscillates  to 
some  extent,  and  is  held  to  relatively  constant  numbers  by  the 
joint  action  of  several  restraining  forces,  we.  see  that  the  re- 
moval or  weakening  of  any  check  or  barrier  is  sufficient  to 
widen  and  intensify  this  dangerous  oscillation ;  may  even  con- 
vert a  perfectly  harmless  species  into  a  frightful  pest.  Wit- 
ness the  maple  bark  louse,  which  is  so  rare  in  natural  forests 
as  scarcely  ever  to  be  seen,  limited  there  as  it  is  by  its  feeble 
locomotive  power  and  the  scattered  situation  of  the  trees  it 
infests.  With  the  multiplication  and  concentration  of  its  food 
in  towns,  it  has  increased  enormously,  and,  if  it  has  not  done 


INSECTS    IN    RELATION    TO    OTHER    ANIMALS  297 

the  g-ravest  injury,  it  is  because  the  trees  attacked  by  it  are  of 
comparatively  sb'ght  economical  value,  and  because  it  has 
finally  reached  new  limits  which  hem  it  in  once  more. 

"  We  are  therefore  sure  that  the  destruction  of  any  species 
of  insectivorous  bird  or  predaceous  insect,  is  a  thing-  to  be 
done,  if  at  all,  only  after  the  fullest  acquaintance  with  the  facts. 
The  natural  presumptions  arc  nearly  all  in  their  favor.  It  is 
also  certain  that  the  species  best  worth  preserving"  are  the 
mixed  feeders  and  not  those  of  narrowly  restricted  dietary 
(parasites,  for  instance), — that  while  the  destruction  of  the 
latter  would  cause  injurious  oscillations  in  the  species  affected 
by  them,  they  afford  a  very  uncertain  safeguard  against  the 
rise  of  such  oscillations.  In  fact,  their  undue  increase  would 
be  finally  as  dangerous  as  their  diminution. 

"  Notwithstanding  the  strong  presumption  in  favor  of  the 
natural  system,  when  we  remember  that  the  purposes  of  man 
and  what,  for  convenience'  sake,  we  may  call  the  purposes  of 
Nature  do  not  fully  harmonize,  we  find  it  incredible  that,  act- 
ing intelligently,  we  should  not  be  able  to  modify  existing  ar- 
rangements to  our  advantage, — especially  since  much  of  the 
progress  of  the  race  is  due  to  such  modifications  made  in  the 
past.  .  .  . 

"■  But  far  the  most  important  general  conclusion  we  have 
reached  is  a  conviction  of  the  general  beneficence  of  nature,  a 
profound  respect  for  the  natural  order,  a  belief  that  the  part 
of  wisdom  is  essentially  that  of  practical  conservatism  in  deal- 
ing with  the  system  of  things  by  which  we  are  surrounded." 

Efficiency  of  Protective  Adaptations  of  Insects. — Inter- 
esting from  a  scientific  point  of  view  are  the  various  adaptations 
by  means  of  which  insects  are  protected  more  or  less  from 
their  bird  enemies.  Colorational  adaptations  having  been  dis- 
cussed in  another  chapter,  there  remain  for  consideration — 
(i)  hairs,  (2)  stings.  (3)  odors,  flavors  and  irritants.  Most 
of  what  follows  is  from  an  admirable  paper  by  Dr.  Judd, 
whose  data  are  based  upon  his  examination  of  the  stomach 
contents  of  fifteen  thousand  birds. 


298  ENTOMOLOGY 

Hairs. — ''  Excepting  two  species  of  cuckoos,  no  species  of 
bird  in  the  eastern  United  States,  so  far  as  I  am  aware,  makes 
a  business  of  feeding  upon  hairy  caterpillars."  Judd  observed 
that  Hyphantria  cunea  infesting  a  pear  tree  was  not  at  all 
molested,  in  spite  of  the  fact  that  the  tree  was  tenanted  by 
three  broods  of  birds  at  the  time,  namely,  kingbirds,  orchard 
orioles  and  English  sparrows.  The  hairy  arctiid  caterpillars, 
however,  are  eaten  by  a  few  birds :  the  robin,  bluebird,  catbird, 
sparro\\--hawk,  cuckoos  and  shrikes ;  and  the  spiny  larvae  of 
Vanessa  antiopa  by  cuckoos  and  the  Baltimore  oriole;  while  the 
hairy  caterpillars  of  the  gypsy  moth  are  known  to  be  eaten  in 
Massachusetts  by  no  less  than  thirty-one  species  of  birds, 
notably  cuckoos,  Baltimore  oriole,  catbird,  chickadee,  blue-jay, 
chipping  sparrow,  robin,  vireos  and  the  crow,  these  birds  be- 
ing of  no  little  assistance  in  the  suppression  of  this  pest. 
These  are  exceptional  cases,  however,  and  in  general  the  hairi- 
ness of  caterpillars  appears  to  be  a  highly  effective  protection 
against  most  birds. 

Stings. — Some  birds  (chewink,  young  ducks)  are  fatally 
affected  by  eating  honey  bees.  The  blue- jays,  however,  will 
eat  Bombiis  and  Xylocopa,  and  flycatchers  and  swallows  feed 
habitually  upon  stinging  Hymenoptera,  particularly  Scoliidse, 
wdiile  a  great  many  birds  eat  Myrmicidae,  or  stinging  ants. 
The  formic  acid  of  ants  does  not  protect  them  from  wholesale 
destruction  by  birds ;  Judd  found  three  thousand  ants  in  the 
stomach  of  a  flicker.  "  Stingless  ants  pretend  to  sting  but 
many  birds  they  do  not  deceive."  The  stinging  caterpillar  of 
Autoincris  io  is  occasionally  eaten  by  the  yellow-billed  cuckoo. 
Aside  from  these  exceptions,  however,  the  stings  of  insects  are 
an  extremely  efficient  means  of  defence. 

Odors,  Flavors  and  Irritants. — The  malodorous  Heterop- 
tera  in  general  are  food  for  most  birds ;  Lygiis,  Reduviid^e  and 
Pentatomidae  are  eaten  by  song  sparrows,  and  Euschisfus  by 
blackbirds  and  crows.  The  odors  of  Heteroptera  are  by  no 
means  universally  protective. 

Among   Coleoptera,   the   showy,    ill-scented   or   ill-flavored 


INSECTS    IN    RELATION    TO    OTHER    ANIMALS  299 

CoccinellicLx  are  eaten  by  but  very  few  birds —  the  flvcatcliers 
and  swallows — and  are  refused  by  caged  blue-jays  and  song 
sparrows  even  when  these  birds  are  hungry.  Of  Chrysomel- 
id?e,  the  Colorado  potato  beetle  is  refused  by  the  catbird,  blue- 
jay  and  song  sparrow,  and  Diabrotica  is  not  often  eaten,  ex- 
cept by  catbirds  and  thrushes.  "  The  smaller  Carabidae, 
whether  stinking  or  not,  are  eaten  by  practically  all  land  birds." 
Crows,  blackbirds  and  jays  eagerly  swallow  Calosouia  scruta- 
tor, and  the  first  two  birds  are  especially  fond  of  Harpalus 
caliginosus  and  H.  pcnnsylvaniciis,  and  feed  Galcrita  to  their 
young.  "  A  score  of  smaller  Carabidse  and  Chrysomelidse, 
metallic  and  conspicuously  colored,  are  habitually  eaten  by 
birds  that  have  an  abundance  of  other  insect  food  to  pick 
from." 

The  stenches  of  Lampyridse  appear  to  be  more  effective 
than  those  of  Carabida;.  Tclephoriis  is  occasionally  eaten,  but 
Photimis  rarely  if  at  all.  Chaiiliognatlms  is  not  eaten  by 
many  birds  (though  flycatchers  and  swallows  select  this  in- 
sect) and  the  genus  is  regarded  unfavorably  by  caged  catbirds 
and  blue-jays. 

In  regard  to  other  insects,  Judd  finds  that  Epicauta,  with  its 
irritant  fluid,  is  immune  from  all  but  the  kingbird;  Cyllene 
seldom  occurs  in  the  stomachs  of  birds ;  May  flies  and  caddis 
flies,  however,  are  terribly  persecuted,  but  swiftly  flying  Dip- 
tera  and  Odonata  are  highly  immune. 

From  such  facts  as  these,  Judd  properly  infers,  "  not  cases 
of  protection  and  non-protection,  but  cases  of  greater  and 
lesser  et^ciency  of  protective  devices." 

2.    The  Transmission  of  Diseases  by  Insects. 

It  is  now  known  that  several  kinds  of  insects  are  of  vital 
importance  to  man  as  agents  in  the  transmission  of  certain 
diseases.  This  recently  demonstrated  role  of  insects  now 
commands  universal  attention. 

Malaria.- — So  far  as  is  known,  malaria  is  transmissible 
only  through  the  agency  of  mosquitoes. 


300 


ENTOMOLOGY 
Fig.  269. 


Life  history  of  malaria  parasite,  Plasmodium  pracox.  i,  sporozoite,  introduced  by- 
mosquito  into  human  blood;  the  sporozoite  becomes  a  schizont.  2,  young  schizont, 
which  enters  a  red  blood  corpuscle.  s>  young  schizont  in  a  red  blood  corpuscle.  4, 
full-grown  schizont,  containing  numerous  granules  of  melanin.  5,  nuclear  division 
preparatory  to  sporulation.  6,  spores,  or  merozoites,  derived  from  a  single  mother- 
cell,  y,  young  macrogamete  (.female),  derived  from  a  merozoite  and  situated  in  a 
red   blood   corpuscle.     7a,   young  microgametoblast    (.male),    derived    from   a    merozoite. 

8,  full-grown  macrogamete.     Sa,   full-grown   microgametoblast.     In    stages  S  and  8a  the 
parasite  is  taken  into  the  stomach  of  a  mosquito;  or  else  remains  in  the  human  blood. 

9,  mature  macrogamete,   capable  of   fertilization;   the  round  black  extruded  object   may 
probably    be    termed    a    "  polar    body."     9a,    mature    microgametoblast,    preparatory    to 


INSECTS    IN    RELATION    TO    OTHER    ANIMALS  3OI 

1"hc  malaria  "germ,"  discoxercd  in  iS8o  by  tlie  French 
army  surgeon  Laveran.  may  1)C  found  as  a  pale.  auKjeboid 
organism  (PlasiiKn^iinn,  Fig.  269)  in  the  red  blood  corpus- 
cles of  persons  aillicted  with  the  disease.  This  organism 
{Silil::::'iif,  J)  grows  at  the  expense  of  the  h;emoglol)in  of  the 
corpuscle  (SS)  and  its  growth  is  accompanied  by  an  increasing 
deposit  of  black  granules  (inelatiin) ,  which  are  doubtless 
excretory  in  their  nature.  At  length,  the  amoebula  divides 
into  many  spores  ( iiicro::;('itcs,  6),  which  by  the  disintegration 
of  the  corpuscle  are  set  free  in  the  plasma  of  the  blood.  Here 
many  if  not  most  of  the  spores,  and  the  pigment  granules  as 
well,  are  attacked  and  absorbed  by  leucocytes,  or  white  blood 
corpuscles,  while  some  of  the  spores  may  invade  healthy  red 
corpuscles  and  develop  as  before.  The  period  of  sporulation, 
as  Golgi  found,  is  coincident  with  that  of  the  "  chill  "  experi- 
enced by  the  patient;  and  quinine  is  most  effective  when  ad- 
ministered just  before  the  sporulation  period.  The  destruc- 
tion of  red  blood  corpuscles  explains  the  pallid,  or  ancvmic, 
condition  which  is  characteristic  of  malarial  patients.  In 
three  or  four  days  the  number  of  red  corpuscles  may  be  re- 
duced from  5,000,000  per  cubic  millimeter — the  normal  num- 
ber— to  3,000,000;  and  in  three  or  four  weeks  of  intermittent 
fever,  even  to  1,000,000. 

Three  types  of  malaria  are  recognized:  (i)  the  tertian,  in 
which  the  paroxysm  recurs  every  two  days;  (2)  the  quartan, 
in  which  it  happens  every  third  day;  and  (3)  the  asstivo- 
autumnal  type   (Fig.  269).     These  three  kinds  are  by  some 

forming  microgametes.  pb,  resting  cell,  bearing  six  flagellate  microgametes  (male). 
10,  fertilization  of  a  macrogamete  by  a  motile  microgamete.  The  macrogamete  next 
becomes  an  ookinete.  //,  ookinete,  or  wandering  cell,  which  penetrates  into  the  wall 
of  the  stomach  of  the  mosquito.  12,  ookinete  in  the  outer  region  of  the  wall  of  the 
stomach,  i.  e.,  next  to  the  body  cavity.  /,•;,  young  oocyst,  derived  from  the  ookinete. 
14,  oocyst,  containing  sporoblasts,  which  are  to  develop  into  sporozoites.  15,  older 
oocyst.  16,  mature  oocyst,  containing  sporozoites,  which  are  liberated  into  the  body 
cavity  of  the  mosquito  and  carried  along  in  the  blood  of  the  insect.  17,  transverse 
section  of  salivary  gland  of  an  Anopheles  mosquito,  showing  sporozoites  of  the  malaria 
parasite  in  the  gland  cells  surrounding  the  central  canal. 

1-6  illustrate  schi::ogony  (asexual  production  of  spores) ;  7-/6,  sporogony  (sexual 
production  of  spores). 

After  Grassi  and  Leuckart,  by  permission  of  Dr.   Carl  Chun. 


302  ENTOMOLOGY 

investigators  thought  to  be  due  to  different  species  of  para- 
sites; and  when,  as  often  happens,  the  malarial  chill  occurs 
every  day,  this  is  attributed  to  two  sets  of  tertian  amcebulse, 
sporulating  on  alternate  days. 

After  several  successive  asexual  generations,  there  are  pro- 
duced merozoites  which  develop — no  longer  into  schizonts — 
but  into  sexual  forms,  or  gametes.  These  occur  in  red 
blood  corpuscles  either  as  macrogametes  (female,  7,  8)  or  as 
micro gametoblasts  (male,  ya,  8a),  in  which  forms  the  parasite 
is  introduced  into  the  stomach  of  a  mosquito  which  has  been 
feeding  upon  the  blood  of  a  malarial  patient.  The  macro- 
gamete  now  leaves  its  blood  corpuscle  and  becomes  spherical 
(p),  as  does  also  the  microgametoblast  (pa)  ;  but  the  latter  puts 
forth  a  definite  number  {six,  in  P.  prcucox,  pb)  of  flagella, 
or  micro  gametes,  which  separate  off  as  motile  male  bodies, 
capable  of  fertilizing  the  macrogametes.  A  microgamete 
penetrates  a  macrogamete  (10)  and  the  nucleus  of  the  one 
unites  with  that  of  the  other.  The  fertilized  macrogamete  now 
becomes  a  migrating  cell,  or  ookinete  (ii),  which  penetrates 
almost  through  the  wall  of  the  stomach  of  the  mosquito  (12) 
and  then  becomes  a  resting  cell,  or  cyst.  This  oocyst  (ij) 
grows  rapidly  and  its  contents  develop,  by  direct  nuclear  divis- 
ion, into  sporoblasts  {14,  ij),  which  differentiate  into  spindle- 
shaped  sporozoites  (16,  i).  The  sporozoites  are  liberated  into 
the  body  cavity  of  the  mosquito,  carried  in  the  blood  to  the  sali- 
vary glands  (as  well  as  elsewhere)  and  thence  along  the  hypo- 
pharynx  into  the  body  of  a  human  being,  bird  or  other  animal 
attacked  by  the  insect. 

The  role  of  the  mosquito  as  the  intermediary  host  of  mala- 
rial organisms  was  discovered  by  Manson  and  Ross  and  con- 
firmed by  Koch,  Sternberg  and  others.  It  has  been  found 
repeatedly  that  certain  mosquitoes  (Anopheles)  after  feeding 
on  the  blood  of  a  malarial  patient  can  transmit  the  disease  by 
means  of  their  "  bites  "  to  healthy  persons.  Thus,  Anopheles 
mosquitoes  were  fed  on  the  blood  of  malarial  subjects  in  Rome 
and  then  sent  to  London,  where  a  son  of  Dr.  Alanson  allowed 


INSECTS    IN    RELATION    TO    OTHER    ANIMALS  3O3 

himself  to  be  bitten  by  the  insects.  Thoug-h  previously  free 
from  the  malarial  org-anism.  he  contracted  a  well-marked 
infection  as  the  result  of  the  inoculation. 

Furthermore,  it  is  hig-hly  probable  that  malaria  cannot  be 
transmitted  to  man  except  throug-h  the  agency  of  the  mos- 
quito. This  appears  from  the  oft-cited  exi)eriment  of  Doc- 
tors Sambon  and  Low  on  the  Roman  Campag-na,  a  place 
notorious  for  malaria.  There  the  experimenters  lived  during 
the  malarial  season  of  1900,  freely  exposed  to  the  emanations 
of  the  marsh  and  taking-  no  precautions  except  to  screen 
their  house  carefully  against  mosquitoes  and  to  retire  indoors 
before  the  insects  appeared  in  the  evening.  Simply  by  ex- 
cluding Anopheles  mosquitoes,  with  which  the  Campagna 
swarmed,  these  investigators  remained  perfectly  immune  from 
the  malaria  which  was  ravaging  the  vicinity. 

In  a  later  experiment  on  the  island  of  Formosa,  one  com- 
pany of  Japanese  soldiers  was  protected  from  mosquitoes  and 
suffered  no  malaria,  while  a  second  and  unprotected  company 
contracted  the  disease. 

The  evident  preventive  measures  to  be  taken  against  ma- 
laria are  ( i )  the  avoidance  of  mosquito  bites,  by  means  of 
screens,  and  washes  of  eucalyptus  oil,  camphor,  oil  of  penny- 
royal, oil  of  tar,  etc.,  applied  to  exposed  parts  of  the  body; 
(2)  the  isolation  of  malarial  patients  from  mosquitoes,  in 
order  to  prevent  infection;  (3)  the  destruction  of  mosquitoes 
in  their  breeding  places,  especially  by  the  use  of  kerosene  and 
by  drainage.  During  unavoidable  exposure  in  malarious 
regions,  quinine  should  be  taken  in  doses  of  six  to  ten  grains 
during  the  day  at  intervals  of  four  or  five  days  (Sternberg). 

Culex  and  Anopheles. — The  mosquitoes  of  North  America 
number  one  hundred  and  twenty-five  known  species.  Of  these 
only  the  genus  Anopheles  transmits  malaria  to  man.  though  in 
India,  Ross  found  that  Culex  transmits  a  form  of  malaria  to 
sparrows.  These  two  common  genera  are  easily  distinguish- 
able. In  Culex  the  wings  are  clear;  in  Anopheles  they  are 
spotted  with  brown.     In  Culex  when  resting,  the  axis  of  the 


304  ENTOMOLOGY 

body  forms  a  curved  line,  the  insect  presenting  a  luimp-backed 
appearance;  in  Anopheles  the  axis  forms  a  straight  Hne. 
Culex  has  short  maxillary  palpi,  while  in  Anopheles  they  are 
almost  as  long  as  the  proboscis.  The  note  of  the  female 
Anopheles  is  several  tones  lower  than  that  of  Culex,  and  only 
the  female  is  bloodthirsty,  by  the  way.  As  regards  eggs, 
larvae  and  pupae,  the  two  genera  differ  greatly.  The  eggs  of 
Culex  are  laid  in  a  mass  and  those  of  Anopheles  singly;  the 
larvae  of  Culex  hang  from  the  surface  film  of  a  pool  at  an 
angle  of  about  forty-five  degrees,  while  those  of  Anopheles 
are  almost  parallel  with  the  surface  of  the  water  in  which 
they  live. 

The  bite  of  an  Anopheles  is  not  necessarily  injurious,  of 
course,  unless  the  insect  has  had  recent  access  to  a  malarious 
person.  Anopheles  may  be  present  where  there  is  no  malaria. 
On  the  other  hand,  it  has  been  found  impossible  to  prove  that 
malaria  exists  where  there  are  no  Anopheles  mosquitoes. 
Finally,  fevers  are  sometimes  diagnosed  as  malarial  which  are 
not  so. 

Possibly  the  malarial  parasite  can  complete  its  cycle  of 
development  in  other  animals  than  man.  It  is  also  possible 
that  originally  the  malarial  organism  was  derived  by  mos- 
quitoes from  the  stems  or  other  parts  of  aquatic  plants,  and 
that  its  effects  on  man  are  incidental  phenomena. 

Yellow  Fever. — It  has  now  been  demonstrated  that  the 
dreaded  disease,  yellow  fever,  is  transmitted  from  one  human 
being  to  another  by  the  bite  of  a  mosciuito  (Stegoniyia  fas- 
ciata)  and  in  no  other  way  excepting,  of  course,  by  the  arti- 
ficial injection  of  diseased  blood.  The  discovery  of  the  mode 
of  transmission  of  the  disease  was  made  in  Cuba  during  1900 
and  1902  by  Dr.  Reed  and  his  corps  of  United  States  army  sur- 
geons. These  investigators  succeeded  in  transmitting  the  dis- 
ease to  healthy  subjects  by  inoculation  from  mosquitoes  which 
had  previously  fed  on  the  blood  of  yellow  fever  patients.  To 
convey  the  disease,  however,  a  period  of  ten  to  thirteen 
days  was  necessary  between  the  original  biting  of  a  patient 


INSECTS    IN    RELATION    TO    OTHER    ANIMALS  3O5 

and  the  inoculation  of  a  healthy  subject.  The  disease  fol- 
lowed the  l)ite  of  an  infected  Stci^oiiiyia  with  remarkable 
precision. 

Furthermore,  Dr.  Reed  and  his  associates  found  that  yel- 
low fever  could  not  be  conveyed  by  means  of  the  clothing, 
bedding,  etc.,  of  fever  patients,  so  long  as  mosquitoes  were 
excluded.  In  the  absence  of  the  mosquito  the  yellow  fever 
patient  is  harmless  and  in  the  absence  of  a  patient  the  mos- 
quito is  harmless  (Sternberg).  The  disease  terminates  in 
cold  weather  with  the  disappearance  of  the  mosquito. 

Preventive  measures  based  upon  these  recently  acquired 
facts  have  been  wonderfully  successful.  The  city  of  Havana, 
in  which  yellow  fever  had  always  prevailed,  has  now  been 
freed  of  the  disease. 

The  specific  cause  of  yellow  fever  has  as  yet  eluded  detec- 
tion in  the  human  body.  There  has  been  discovered,  how- 
ever, in  the  stomach  and  salivary  glands  of  mosquitoes  in- 
fected with  yellow  fever,  a  protozoan  parasite  (order  Coc- 
cidiida),  the  sexual  cycle  of  wdiich,  ending  in  the  development 
of  sporozoites,  has  been  traced  in  the  body  of  the  Stcgomyia. 
This  coccidium  may  or  may  not  prove  to  be  concerned  in  the 
transmission  of  the  disease. 

Other  Diseases. — Typhoid  fever  is  transmitted  frequently 
by  the  common  house  fly,  which  may  carry  the  bacillus  from 
the  excreta  of  typhoid  patients  to  food  supplies  in  kitchens  or 
elsewhere.  The  spread  of  the  disease  in  army  camps  is  due 
chiefly  to  the  house  fly  {Miisca  doniestica) ,  as  was  demon- 
strated in  1898  by  a  commission  of  the  United  States  army. 

The  dreaded  disease  filariasis  (elephantiasis)  of  Oriental 
tropical  regions  is  transmitted  by  mosquitoes  of  the  genus 
Culex,  as  Dr.  Manson  discovered  many  years  ago.  The  dis- 
ease is  due  to  a  parasitic  worm  (Filaria) ,  both  sexes  of  which 
lodge  in  the  lymphatic  vessels,  obstruct  the  flow  of  the  lymph 
and  thereby  cause  an  abnormal  enlargement  of  the  parts  in 
which  they  occur.  The  embryos  of  the  parasite  pass  into  the 
blood  and  thence  into  the  body  of  the  mosquito ;  there  they 


306  ENTOMOLOGY 

remain  in  the  thoracic  muscles  for  a  time  and  become  larvae, 
which  at  length  pass  through  the  proboscis  of  the  mosquito 
into  the  skin  of  man.  It  is  possible,  though  not  proved,  that 
other  mosquitoes  than  Cnlex  and  indeed  other  kinds  of  insects 
are  involved  in  the  transmission  of  filariasis. 

In  Egypt,  an  eye  disease  is  transmitted  by  the  house  fly. 
There  is  some  evidence  that  the  bubonic  plague  is  spread 
through  the  agency  of  fleas.  Anthrax  of  cattle  is  carried  by 
gad  flies  (Tabanidse).  A  South  African  disease  fatal  to 
horses,  cattle  and  dogs,  though  not  to  man,  is  transmitted 
from  infected  to  healthy  animals  by  the  proboscis  of  a  muscid 
fly,  Glossina  morsitans,  as  has  been  mentioned.  The  specific 
cause  of  this  disease  is  a  blood  parasite  similar  to  that  of 
malaria.  Finally,  the  destructive  Texas  fever  of  cattle  is 
undoubtedly  transmitted  by  the  common  cattle-tick,  as  was 
discovered  by  Theobald  Smith,  though  the  tick  is  not,  properly 
speaking,  an  insect. 


CHAPTER    X 


INTERRELATIONS    OF    INSECTS 


Fig.  270. 


Insects  in  general  are  adapted  to  utilize  all  kinds  of  organic 
matter  as  food,  and  they  show  all  gradations  of  habit  from 
herl)ivorons  to  carni\-orons.  The  many  forms  that  derive 
their  food  from  the  bodies  of  other  insects  may  conveniently 
be  classed  as  predaceons  or  parasitic. 

Predaceous  Insects. — Among  Orthoptera,  Mantidse  are 
nota1)ly  predatory,  their  front  legs  (Fig.  62,  C)  being  well 
fitted  for  grasping  and  killing  other  insects.  The  predaceous 
odonate  nymphs  have  a  peculiar 
hinged  extensible  labium  Avith 
which  to  gather  in  the  prey.  The 
adults  catch  with  surpassing 
speed  and  precision  a  gTeat  va- 
riety of  flying  insects,  mostly 
small  forms,  but  occasionally  but- 
terflies of  considerable  size.  The 
eyes  of  a  dragon  fly  are  remark- 
ably large ;  the  legs  form  a  spiny 
basket,  probably  to  catch  the  prey, 
which  is  instantly  stripped  and 
devoured,  these  operations  being 
facilitated  by  the  excessive  mobil- 
ity of  the  head.  The  hemipter- 
ous  families  Corixidse,  Notonect- 
id?e    (Fig.  224).  Nepidse,  Belos- 

tomid?e  (Fig.  22),  Naucoridae  (Fig.  62,  D),  Reduviidae  and 
Phymatidje  are  predaceous,  with  raptorial  front  legs  and  sharp 
beaks.  Some  of  the  Pentatomidse  (Fig.  270)  are  of  con- 
siderable economic  value  on  account  of  their  predaceous 
habits.     Most    of    the    Xeuroptera    feed    upon    other    insects. 

307 


Nymph  of  Podisiis  spiitosus  suck- 
ing the  blood  from  a  clover  cater- 
pillar, Colias  philodice.  Natural 
size. 


308  ENTOMOLOGY 

The  My  nucleoli  larva  digs  a  funnel-shaped  pitfall,  at  the  bot- 
tom of  which  it  bnries  itself  to  await  the  fall  of  some  unlucky 
ant.  The  Chrysopa  larva  impales  an  aphid  on  the  points  of 
its  mandibles  and  sucks  the  blood  through  a  groove  along 
each  mandible  (Fig.  45,  E),  the  maxilla  fitting  against  this 
groove  to  form  a  closed  channel.  Several  families  of  Coleop- 
tera  are  almost  entirely  predaceous.  Among  aquatic  beetles, 
Dytiscidae  are  carnivorous  both  as  larv?e  and  imagines,  Gyrin- 
idse  subsist  chiefly  upon  disabled  insects,  but  occasionally  eat 
plant  substances,  and  Hydrophilid^e  as  larvae  catch  and  devour 
other  insects,  though  some  of  the  beetles  of  this  family  {H. 
triangularis,  for  example,  Fig.  226)  feed  largely  if  not  en- 
tirely upon  vegetation.  Of  terrestrial  Coleoptera,  the  tiger 
beetles  (Cicindelidje)  are  strictly  predaceous  upon  other  insects. 
The  Cicindcla  larva  lives  in  a  burrow  in  the  soil  and  lies  in 
wait  for  passing  insects ;  a  pair  of  hooks  on  the  fifth  segment 
of  the  abdomen  serves  to  prevent  the  larva  from  being  jerked 
out  of  its  burrow  by  the  struggles  of  its  captive.  The  large 
family  Carabidae  is  chiefly  predaceous ;  these  "  running 
beetles  "  both  as  larvee  and  adults  easily  overtake  and  capture 
other  terrestrial  insects.  The  Carabid^e,  however,  are  by  no 
means  exclusively  carnivorous,  for  many  of  them  feed  to  some 
extent  upon  fungus  spores,  pollen,  ovules,  root-tips  and  other 
vegetable  matter,  as  Forbes  has  found;  Harpalus  caliginosus 
eats  the  pollen  of  the  ragweed  in  autumn ;  Galerita  janiis  eats 
caterpillars  and  occasionally  the  seeds  of  grasses;  Calosoma, 
however,  appears  to  be  strictly  carnivorous,  feeding  chiefly 
upon  caterpillars  and  being  in  this  respect  of  considerable  eco- 
nomic importance.  As  a  whole,  Carabidse  prefer  animal  food, 
as  appears  from  the  fact  that  when  canker  worms,  for  in- 
stance, are  unusually  abundant  they  form  a  correspondingly 
large  percentage  of  carabid  food,  the  increase  being  compen- 
sated by  a  diminution  in  the  amount  of  vegetable  food  taken 
(Forbes).  Coccinellid  larvce  (excepting  Epilachna,  which 
eats  leaves)  feed  almost  entirely  upon  plant  lice  and  consti- 
tute one  of  the  most  effective  checks  upon  their  multiplication ; 


INTERRELATIONS    OF    INSECTS  3O9 

the  beetles  eat  aphides,  but  also  fungus  spores  and  pollen  in 
large  quantities.  Though  Lepidoptera  are  pre-eminently  phy- 
tophagous, the  larva  of  Feniscca  tarqidnius  is  unique  in  feeding 
solely  upon  plant  lice,  particularly  the  woolly  Schiconcura  tes- 
scllata  of  the  alder.  Among  Diptera,  Asilida^,  Midaidse, 
Therevidse  and  Empidida^  are  the  chief  predaceous  families. 
Asilidae  ferociously  attack  not  only  other  flies,  but  also  beetles, 
bumble  bees,  butterflies  and  dragon  flies ;  as  larvae  they  feed 
largely  upon  the  larvse  of  beetles.  Many  of  the  larvae  of 
Syrphidse  prey  upon  plant  lice,  and  the  larvae  of  Volucclla  feed 
in  Europe  on  the  larvK  of  bumble  bees  and  wasps.  Of 
Hymenoptera,  the  ants  are  to  a  great  extent  predaceous, 
attacking  all  sorts  of  insects,  but  particularly  soft-bodied 
kinds;  while  Vespidae  feed  largely  upon  other  insects,  though 
like  the  ants,  they  are  fond  of  the  nectar  of  flowers  and  the 
juices  of  fruits. 

Parasitic  Insects. — Though  very  many  insects  occur  as 
external  parasites  on  the  bodies  of  birds  and  mammals,  very 
few  occur  as  such  on  the  bodies  of  other  insects ;  one  of  the 
few  is  Braula  cccca,  a  wingless  dipteron  found  on  the  body 
of  the  honey  bee. 

A  vast  number  of  insects,  however,  undergo  their  larval 
development  as  internal  parasites  of  other  insects,  and  most 
of  these  parasites  belong  to  the  two  most  specialized  orders, 
Diptera  and  Hymenoptera. 

The  larvae  of  Bombyliidae  feed  upon  the  eggs  of  Orthop- 
tera  and  upon  larvae  of  Lepidoptera  and  Hymenoptera. 
Tachinidae  are  the  most  important  dipterous  parasites  of  other 
insects  and  lay  their  eggs  most  frequently  upon  caterpillars ; 
the  larvae  bore  into  their  victim,  develop  within  its  body,  and 
at  length  emerge  as  winged  insects.  These  parasites  often 
render  an  important  service  to  man  in  checking  the  increase 
of  noxious  Lepidoptera. 

The  great  majority  of  insect  parasites — many  thousand 
species — belong  to  the  order  Hymenoptera,  constituting  one 
of  the  primary  divisions  of  the  order.     They  are  immensely 


3IO 


ENTOMOLOGY 


important  from  an  economic  standpoint,  particularly  the  Ich- 
neumonid?e,  of  which  more  than  ten  thousand  species  are  al- 
ready known.  Our  most  conspicuous  ichneumonids  are  the 
two  species  of  Thalessa,  T.  atrata  and  T.  lunator  (Fig.  271), 
with  their  long  ovipositors  (three  inches  long  in  lunator,  and 

Fig.  271. 


Oviposition   of   Thalessa   lunator.     Natural    size. — After    Riley. 

four  to  four  and  three  Cjuarters  inches  in  atrata).  Thalessa 
bores  into  the  trunks  of  trees  in  order  to  reach  the  burrows  of 
another  large  hymenopteron,  Tremex  coluinba  (Fig.  31),  upon 
whose  larvae  the  larva  of  Thalessa  feeds. 

The  enormous  family  Braconidre,  closely  related  to  Ichneu- 
monidcT,  is  illustrated  by  the  common  Apantcles  congregatiis, 
which  lays  its  eggs  in  the  caterpillars  of  various  Sphingidae. 
The  parasitic  larvae  feed  upon  the  blood  and  possibly  also  the 
fat-body  of  their  host,  and  at  length  emerge  and  spin  their  co- 
coons upon  the  exterior  of  the  caterpillar  (Fig. 272), sometimes 
to  the  number  of  several  hundred.  Species  of  Aphidius  trans- 
form within  the  bodies  of  plant  lice,  one  to  each  host,  and  the 
imago  cuts  its  way  out  throug'h  a  circular  opening  with  a  cor- 
respondingly circular  lid.  Chalcididae,  of  which  some  four 
thousand  species  are  know^n,  are  usually  minute  and  parasitic; 


INTERRELATIONS    OF    INSECTS 


311 


thoiii^h  some  are  phytophagous,  for  example,  Isosoma  hordei, 
which  Hves  in  the  stems  of  grasses,  especially  wheat,  rye  and 
harlcy.  Chalcids  affect  a  gTeat  variety  of  insects  of  one  stage 
or  another,  such  as  caterpillars,  pup;e.  cockroach  eggs,  plant 
lice  and  scale  insects;  while  some  of  them  develop  in  cynipid 
galls,  either  upon  the  larvcC  of  the  gall-makers  or  upon  the 
larvas  of  inquilines.  Giard  in  France  reared  more  than  three 
thousand  chalcids   {Copidosoma  tnnicatcllinn)   from  a  single 

Fig.   272, 


A  tomato  worm,  Phlcgetltontius  sc.vta,   bearing  cocoons  of  the  parasitic  Apantclcs  con- 
gregaius.      Natural  size. 

caterpillar  of  Plusia.  Proctotrypidae  are  remarkable  as  para- 
sites. Most  of  them  are  minute ;  indeed  this  family  and  the 
coleopterous  family  Trichopterygidae  contain  the  smallest 
winged  insects  known — species  but  one  third  or  one  fourth 
of  a  millimeter  long.  A  large  proportion  of  the  Proctotry- 
pidas  are  parasitic  in  the  eggs  of  other  insects  or  of  spiders, 
several  sometimes  developing  in  the  same  egg;  others  affect 
odonate  nymphs  and  coleopterous  or  dipterous  larvse,  while 
several  species  have  been  reared  from  cecidomyiid  and  cynipid 
galls,  and  many  proctotrypids  are  parasites  of  other  parasitic 
insects — -in  other  words,  are  liyperparasitcs. 


3  I  2  ENTOMOLOGY 

Hyperparasitism. — Not  only  are  primary  parasites  fre- 
quently attacked  by  other,  or  secondary,  parasites,  but  tertiary 
parasitism  is  known  to  occur  in  a  few  instances,  and  there  is 
some  reason  to  believe  that  even  the  quaternary  type  exists 
among  insects,  as  in  the  following  case. 

The  caterpillar  of  Hernerocampa  (Orgyia)  leucostigma 
defoliates  shade  trees  in  the  northeastern  United  States.  An 
enormous  increase  of  this  species  in  the  city  of  Washington  in 
1895  was  attended  by  a  corresponding  increase  of  parasitic 
and  predaceous  species,  and  this  unusual  opportunity  for  the 
study  of  parasitism  was  made  the  most  of  by  Dr.  Howard, 
from  whose  admirable  paper  these  facts  are  taken. 

The  primary  parasites  of  H.  leucostigma  numbered  23  spe- 
cies— 17  Hymenoptera  and  6  Diptera;  of  the  hyperparasites 
(all  hymenopterous)  13  were  secondary,  2  and  probably  5 
were  tertiary,  and  one  of  these  (Asecodes  albitarsis)  may  un- 
der certain  conditions  prove  to  be  a  quaternary  parasite.  To 
illustrate — The  ichneumon  Piuipla  inquisitor,  an  important 
primary  parasite  of  lepidopterous  larvae,  lays  its  eggs  in  cater- 
pillars of  H.  leucostigma;  its  larvae  suck  the  blood  of  their 
host  and  at  length  spin  their  cocoons  within  the  loose  cocoon 
of  the  Henicrocanipa.  These  cocoons  have  yielded  a  well- 
known  secondary  parasite,  the  chalcid  Dibrachys  bouchcanus. 
Now  another  chalcid,  Asecodes  albitarsis,  has  been  seen  to  issue 
from  a  pupa  of  this  Dibrachys,  thus  establishing  tertiary  para- 
sitism. Furthermore,  it  is  quite  possible  that  Dibrachys  itself 
is  a  tertiary  parasite,  in  which  event  the  Asecodes  might  be- 
come a  parasite  of  the  quaternary  order. 

Economic  Importance  of  Parasitism. — If  a  primary  para- 
site is  beneficial,  its  own  parasites  are  indirectly  injurious,  gen- 
erally speaking;  while  those  of  the  third  and  the  fourth  order 
are  respectively  beneficial  and  injurious.  The  last  two  kinds 
are  so  rare,  however,  as  to  be  of  no  practical  importance  from 
an  economic  standpoint.  The  first- two  kinds  are  of  immense 
economic  importance,  particularly  the  primary  parasites. 
"  Outbreaks  of  injurious   insects,"   says   Howard,   "  are   fre- 


INTERRELATIONS    OF    INSECTS  3  13 

qiiently  stopped  as  thout^li  by  magic  l)y  the  work  of  insect  ene- 
mies of  the  species.  llnl)bard  found,  in  icSSo,  that  a  minute 
parasite,  Trichograiiiiiia  prctiosa,  alone  and  unaided,  ahnost 
annihilated  the  fifth  brood  of  the  cotton  worm  in  Morida,  fully 
ninety  per  cent,  of  the  eggs  of  this  prolific  crop  enemy  being 
infested  by  the  parasite.  Not  longer  ago  than  1895,  in  the 
city  of  Washington,  more  than  ninety-seven  per  cent,  of  the 
caterpillars  of  one  of  our  most  important  shade-tree  pests 
[Orgyia,  as  just  mentioned]  were  destroyed  by  parasitic  in- 
sects, to  the  complete  relief  of  the  city  the  following  year. 
The  Hessian  fly,  that  destructive  enemy  to  wheat  crops  in  the 
United  States,  is  practically  unconsidered  by  the  wheat  grow- 
ers of  certain  states,  for  the  reason  that  wdienever  its  numbers 
begin  to  be  injuriously  great  its  parasites  increase  to  such  a 
degree  as  to  prevent  appreciable  damage. 

"  The  control  of  a  plant-feeding  insect  by  its  insect  enemies 
in  an  extremely  complicated  matter,  since,  as  we  have  already 
hinted,  the  parasites  of  the  parasites  play  an  important  part. 
The  undue  multiplication  of  a  vegetable  feeder  is  followed  by 
the  undue  multiplication  of  parasites,  and  their  increase  is  fol- 
lowed by  the  increase  of  hyperparasites.  Following  the  very 
instance  of  the  multiplication  of  the  shade-tree  caterpillar  just 
mentioned,  the  writer  [Howard]  was  able  to  determine  this 
parasitic  chain  during  the  next  season  down  to  cjuaternary 
parasitism.  Beyond  this  point,  true  internal  parasitism  prob- 
ably did  not  exist,  but  even  these  quaternary  parasites  were 
subject  to  bacterial  or  fungus  disease  and  to  the  attacks  of 
predatory  insects. 

"  The  prime  cause  of  the  abundance  or  scarcity  of  a  leaf- 
feeding  species  is,  therefore,  obscure,  since  it  is  hindered  by 
an  abundance  of  primary  parasites,  favored  by  an  abundance 
of  secondary  parasites  (since  these  will  destroy  the  primary 
parasites),  hindered  again  by  an  abundance  of  tertiary  para- 
sites, and  favored  again  by  an  abundance  of  quaternary  para- 
sites." 

Entomologists   have  made  many  attempts   to   import   and 


314  ENTOMOLOGY 

propagate  insect  enemies  of  various  introduced  insect  pests, 
and  some  of  their  etTorts  have  been  crowned  with  success,  as 
was  notably  the  case  when  Novius  cardinalis,  a  lady-bird 
beetle,  was  taken  from  Australia  to  California  to  destroy  the 
fluted  scale. 

Form  of  Parasitic  Larvae. — The  peculiar  environment  of 
parasitic  larvae  is  responsible  for  profound  changes  in  their 
organization.  These  larvae,  in  general,  are  apodous,  the  body 
is  compact  and  the  head  is  more  or  less  reduced,  sometimes  to 
the  merest  rudiment.  These  characters,  occurring  also  in  such 
dipterous  larvae  as  live  in  a  mass  of  decaying  organic  matter 
and  again  in  those  hymenopterous  larvae  whose  food  is  pro- 
vided by  the  mother  or  by  nurses,  are  to  be  attributed  to  the 
presence  of  a  plentiful  supply  of  food,  obtainable  with  little  or 
no  exertion,  and  indicate,  not  primitive  simplicity  of  organiza- 
tion, but  a  high  degree  of  specialization,  as  we  have  said  before. 
The  embryonic  development  of  parasitic  larvae  is  frequently 
highly  anomalous,  as  appears  in  the  chapter  on  development. 

Maternal  Provision. — Excepting  several  families  of  Hy- 
menoptera  and  the  Termitidae,  few  insects  make  any  special 
provision  for  the  welfare  of  the  young  beyond  laying  the  eggs 
in  some  appropriate  situation.  Many  insects,  as  walking- 
sticks  (Phasmidae)  and  May  beetles  {Lachnosterna)  simply 
drop  their  eggs  to  the  ground,  leaving  the  young  to  shift  for 
themselves.  Most  insects,  however,  instinctively  lay  their 
eggs  in  situations  where  the  larva  is  sure  to  find  its  proper  food 
near  at  hand.  Thus  various  flies  and  beetles  deposit  their  eggs 
on  decaying  animal  matter,  butterflies  and  moths  are  more  or 
less  restricted  to  particular  species  of  plants,  and  parasitic 
Hymenoptera  to  certain  species  of  insects.  The  beetles  of  the 
genus  Nccrophonis  go  so  far  as  to  bury  the  body  of  a  bird, 
mouse  or  other  animal  in  which  the  eggs  are  to  be  laid;  and 
in  this  instance  the  male  assists  the  female  in  undermining  and 
afterward  co^•ering  the  body.  A  similar  co-operation  of  the 
two  sexes  occurs  in  the  scarabaeid  beetles  known  as  "  tumble- 
bugs,"  a  pair  of  which  may  often  be  seen  rolling  along  labori- 


INTERRELATIONS    OF    INSECTS  315 

ously  a  ball  of  dung  which  is  to  serve  as  larval  food.  The 
female  mole-cricket  (Gryllolalpa)  is  said  to  care  for  her  eggs 
and  even  to  feed  the  young  at  first. 

Hymenoptera  display  all  degrees  of  complexity  in  regard  to 
maternal  provision.  Tenthredinidse  simply  lay  their  eggs  on 
the  proper  food  plants  or  else  insert  them  into  the  tissues  of 
the  plants.  Sphecina  make  a  nest,  provision  it  with  food  and 
leave  the  young  to  care  for  themselves.  Queen  wasps  and 
•  bumble  bees  go  a  step  further  in  feeding  the  first  larvae  and 
carrying  them  to  maturity.  Finally,  in  the  honey  bee  the  care 
of  the  young  is  at  once  relegated  by  the  queen  to  other  individ- 
uals of  the  colony,  as  is  also  the  case  among  ants. 

Some  of  the  most  elaborate  examples  of  purely  maternal 
provision  are  found  among  the  digger  wasps  and  the  solitary 
wasps ;  these  instances  are  highly  interesting,  involving  as  they 
do  an  intricate  co-ordination  of  many  refiex  actions — as  ap- 
pears in  the  discussion  of  insect  behavior. 

Among  the  Sphecina,  or  digger  wasps,  the  female  makes  a 
nest  by  burrowing  into  the  ground,  by  mining  into  such  pithy 
plants  as  elder  or  sumach,  or  else  by  plastering  bits  of  mud 
together.  The  nest  is  provisioned  with  insects  or  spiders 
which  have  been  stung  in  such  a  way  as  usually  to  be  para- 
lyzed, without  being  actually  killed.  The  various  species  of 
Sphecina  frequently  select  particular  species  of  insects  or 
spiders  as  food  for  the  young.  Pepsis  formosa  (Pompilidae) 
uses  tarantulas  for  this  purpose;  Splicciits  speciosus  (Bembe- 
cidse)  stores  her  nest  with  a  cicada;  Nyssonidse  pick  out  cer- 
tain species  of  Membracidoe ;  mud-daubers  (Sphecidcx)  use 
spiders;  and  other  families  of  Sphecina  capture  bees,  beetles, 
plant  lice  or  other  insects,  as  the  case  may  be.  The  solitary 
wasps  (Eumenidae)  are  similar  to  the  digger  wasps  in  habits. 

Of  the  solitary  bees,  Megocliile  is  well  known  for  its  habit 
of  cutting  pieces  out  of  rose  leaves;  it  uses  oblong  pieces  to 
form  a  thimble-shaped  tube  which,  after  being  stored  with  pol- 
len and  nectar,  is  plugged  with  a  circular  piece  of  leaf.  The 
larval  cells  are  made  either  in  tunnels  excavated  in  wood  by 
the  mother  or  else  in  cracks  or  other  chance  cavities. 


3i6 


ENTOMOLOGY 


One  of  the  carpenter  bees,  Ccratina  dupla,  which  builds  in 
the  hollow  stem  of  a  plant  a  series  of  larval  cells  separated  by 
partitions,  is  said  by  Comstock  to  watch  over  her  nest  until 
the  young  mature. 

The  transition  from  the  solitary  to  the  social  habit  is  indi- 
cated in  the  life-histories  of  wasps  and  bumble  bees,  where  a 
solitary  queen  founds  the  colony  but  soon  relegates  to  other 
individuals  all  duties  except  that  of  egg-laying.  The  social 
insects  will  now  be  considered. 

Termites 
Though  popularly  known  as  "  white  ants,"  the  termites  are 
quite  different  from  true  ants,  being  indeed  not  very  far  re- 
moved from  the  most  primitive  insects.  In  view  of  the  ex- 
treme contrast  in  structure  and  development  between  termites 
and  ants,  it  is  remarkable  that  the  two  groups  should  have 
much  the  same  kind  of  complex  social  organization. 

Fig.  272,. 


Various  forms  of  Terincs  lucifugus.  A,  adult  worker;  B,  soldier;  C,  perfect  winged 
insect;  D,  perfect  insect  after  shedding  the  wings;  E,  young  complementary  queen; 
F,   older  complementary  queen.     Enlarged. — After   Grassi    and   Sandias. 

Classes  of  Termites. — In  general,  four  kinds  of  adults  are 
produced  in  a  community  of  termites,  namely — workers,  sol- 
diers, zvingcd  males  and  unnged  females. 

The  workers  (Fig.  273,  A),  which  are  ordinarily  the  most 
numerous,  are  of  either  sex,  but  their  reproductive  organs  are 
undeveloped.     A   worker-ant   or   bee,   however,    is   always   a 


INTERRELATIONS    OF    INSECTS 


1^7 


Fig. 


female.  The  termite  workers,  as  the  name  imphes,  do  most 
of  the  work;  they  make  the  nest,  provide  food,  feed  and  care 
for  the  young  and  the  royal  pair,  and  attend  to  many  other 
domestic  duties. 

The  soldiers,  like  the  workers,  are  of  either  sex,  with  unde- 
veloped sexual  organs.  With  monstrous  mandibles  and  head 
(Fig.  273,  B),  their  chief  duty  apparently 
is  to  defend  the  colony,  though  they  fre- 
quently fail  to  do  so. 

The  winged  males  and  females  (Fig. 
273.  C)  which  are  sexually  mature, 
swarm  from  the  nest  and  mate.  After 
the  nuptial  flight  the  pair  burrow  into 
some  crevice  and  shed  the  wings,  which 
break  off  each  along  a  peculiar  transverse 
suture,  leaving  four  triangular  stumps 
(Fig.  273,  D).  The  king  and  queen 
found  a  new  colony  and  may  live  for 
scA'cral  years,  sheltered  in  a  special  cham- 
ber, the  queen,  meanwdiile,  becoming 
enormously  distended  (Fig.  274)  with 
eggs  and  almost  incapable  of  locomotion. 
The  prolificacy  of  the  queen  is  astonish- 
ing; she  can  lay  thousands  of  eggs, 
sometimes  at  the  rate  of  sixty  per  minute. 
She  is  the  nucleus  of  the  colony,  and 
should  she  become  incapacitated,  is  replaced  by  one  or  more 
substitute  queens,  which  have  been  developed  to  meet  the  emer- 
gency; similarly,  a  substitute  king  is  matured  upon  occasion. 
These  substitutes  (Fig.  273,  E)  differ  from  the  primary  pair 
in  having  nymphal  wing-pads  in  place  of  the  remains  of  func- 
tional wings. 

These  six  kinds  are  by  no  means  all  that  may  occur  in  a 
single  colony.  Tennes  lucifugus,  according  to  Grassi,  has  no 
less  than  fifteen  kinds  of  individuals,  counting  nymphs  in  vari- 
ous stages  of  development  toward  workers,  soldiers,  and  pri- 
mary or  else  complementary,  or  reserve,  kings  or  queens. 


Queen  of  Tcrines  obc- 
sus.  Natural  size. — After 
Hagen". 


3l8  ENTOMOLOGY 

Origin  of  Castes. — Grassi  maintains  that  all  the  forms  are 
alike  at  birth  except  as  reg-ards  sex,  and  that  the  differences 
between  worker  and  soldier,  which  are  independent  of  sex, 
depend  probably  upon  nutrition.  Grassi  attributes  all  the  di- 
versities of  caste,  except  the  sexual  ones,  to  the  character  and 
amount  of  the  food. 

Food. — The  food  of  termites  is  of  six  kinds  :  ( i )  wood  ; 
(2)  matter  emitted  from  the  oesophag-us  or  rectum,  termed 
respectively  stomodseal  and  proctodfeal  food;  (3)  cast  skins 
and  other  exuvial  stuff;  (4)  the  bodies  of  their  companions; 
(5)  saliva;  (6)  water.  Of  these  the  proctodaeal  food  is  the 
favorite.  Nymphs  receive  at  first  only  saliva ;  later  they  get 
stomodseal  and  proctod?eal  food  until,  finally,  they  are  able  to 
eat  wood — the  staple  food  of  a  termite. 

American  Species. — Our  common  termite  is  Termes  Uavi- 
pes,  which  occurs  throughout  the  United  States,  excavating 
its  galleries  in  decaying  logs,  stumps  or  other  dead  wood.  The 
nuptial  flight  of  this  species  takes  place  in  spring,  when  the  two 
sexes  swarm  in  numbers  that  are  sometimes  enormous.  One 
swarm,  as  recorded  by  Hagen,  appeared  as  a  dense  cloud,  and 
was  being  followed  and  attacked  by  no  less  than  fifteen  species 
of  birds,  among  which  were  robins,  bluebirds  and  sparrows ; 
some  of  the  robins  were  so  gorged  to  the  mouth  with  termites 
that  their  beaks  stood  open.  Though  plenty  of  winged  fe- 
males are  said  to  occur  in  the  swarming  season,  a  true  queen 
of  T.  Havipcs  is  as  yet  unknown,  the  queen  described  by  Hub- 
bard being  evidently,  from  her  undeveloped  wings,  a  substitu- 
tion c[ueen. 

In  the  Western  states,  six  species  of  termites  are  known,  in- 
cluding Termes  hieifugus,  which  has  probably  been  introduced 
from  Europe.  In  this  species  the  primary  queen  is  known  to 
exist. '  Regarding  the  Californian  Teniiopsis  angusticollis, 
Dr.  Heath  says  that  if  only  one  of  the  royal  pair  be  destroyed 
usually  only  one  substitution  form  is  developed,  but  when  both 
perish,  from  ten  to  forty  substitutes  appear,  according  to  the 
size   of   the   colony ;    furthermore — a    remarkable    fact — these 


INTERRELATIONS    OF    INSECTS 


319 


substitution  royalties  may  contain   workers  or  even   soldiers 
capable  of  laying  eggs. 

Architecture. — Wbile  many  termites  simply  burrow  in  dead 
wood,  other  species  construct  more  elaborate  nests.  A  Jamai- 
can species  builds  huge  nests  in  the  forks  of  trees,  with  covered 
passageways  leading  to  the  ground. 

In  parts  of  Africa  and  Australia,  where  they  are  free  from 
disturbance,  termites  erect  huge  mounds,  frequently  six  to  ten 
and  sometimes  eighteen  or  twenty  feet  high,  with  galleries 
extending  as  far  below  the 

surface    of    the    ground    as  "  "  ^' 

they  do  above  it.  These  im- 
mense structures  (Fig.  275) 
consist  chiefly  of  earth,  ce- 
mented by  means  of  some 
secretion  into  a  stony  clay, 
with  which  also  much  excre- 
mentitious  matter  is  mixed ; 
they  are  pyramidal,  colum- 
nar, pinnacled  or  of  various 
other  forms,  according  to 
the  species,  and  are  perfor- 
ated by  thousands  of  pass- 
ages and  chambers,  while 
there  are  underground  gal- 
leries extending  away  from 
the  mound  to  a  distance 
of  often  several  hundred 
feet. 

An  extraordinary  type  of  mound  is  constructed  by  the 
"compass,"  or  ''meridian,"  termites  of  North  Australia,  for 
their  wedge-shaped  mounds  (Fig.  276),  commonly  eight  or 
ten  feet  high,  though  sometimes  as  high  as  twenty  feet,  are 
directed  north  and  south  with  surprising  accuracy.  By  means 
of  this  orientation  the  exposure  to  the  heat  of  the  sun  is  re- 
duced to  the  minimum,  as  occurs  also  in  the  case  of  many  Aus- 


rmite   mound,    Kimberley   type,   Australia. 
— After    Saville-Kent. 


320 


ENTOMOLOGY 


Fig.  276. 


tralian  plants,  the  leaves  of  which  present  their  edges  instead 
of  their  faces  to  the  sun. 

More  than  one  species  of  termite  may  inhabit  a  single  nest ; 
in  one  South  African  nest  Haviland  found  five  species  of  ter- 
mites and  three  of  ants.  The 
widely  distributed  genus  Euter- 
nics  is  essentially  a  group  of 
inqiiiline,  or  guest,  species. 
Termite  mounds  afford  shelter 
to  scorpions,  snakes,  lizards, 
rats,  and  even  birds,  some  of 
which  nest  in  them.  The  Aus- 
tralian bushmen  hollow  out  the 
mounds  to  make  temporary 
ovens,  and  even  eat  the  clay  of 
which  they  are  composed,  while 
natives  of  India  and  Africa  are 
accustomed  to  eat  the  termites 
themselves,  the  flavor  of  which 
is  said  to  be  delicious. 

Ravages.  —  In  tropical  re- 
gions the  amount  of  destruc- 
tion done  by  termites  is  enor- 
mous, and  these  formidable 
pests  are  a  constant  source  of 
consternation  and  dread.  They 
emit  a  secretion  that  corrodes 
metals  and  even  glass,  while 
anything  made  of  wood  is  sim- 
ply at  their  mercy.  Always  avoiding  the  light,  they  hollow 
out  floors,  rafters  or  furniture,  leaving  only  a  thin  outer  shell, 
and  as  a  result  of  their  insidious  work  a  chair  or  a  table  may 
unexpectedly  crumble  at  a  touch.  Jamestown,  the  capital  of 
St.  Helena,  was  largely  destroyed  by  termites  (1870)  and  had 
to  be  rebuilt  on  that  account. 

In  the  United  States  and  Europe  few  species  of  termites 


INIound  of  the  "  compass  "  termite 
of  North  Australia. — After  Saville- 
Kent. 


INTERRELATIONS    OF    INSECTS 


321 


occur,  and  they  do  little  injury  as  compared  with  the  tropical 
species;  thong"h  onr  common  Tcniics  flcn'ipcs  occasionally 
damages  woodwork,  hooks,  plants,  etc..  in  an  extensive  way, 
particularly  in  the  Southern  states. 

Termitophilism. — Associating  with  termites  are  found 
various  other  arthropods,  mostly  insects.  Their  relations  to 
the  termites  are,  so  far  as  is  known,  similar  to  those  described 
beyond  between  myrmecophilous  species  and  ants.  These 
tcnniiopJiilous  forms.  howe\'er,  have  recei\'ed  as  yet  but  little 
attention. 

Honey  Bee 

For  more  than  three  thousand  years  the  honey  bee  has  been 
almost  unique  among  insects  as  an  object  of  human  care  and 
study.  It  was  highly  prized  by  the  old  Greeks  and  Romans 
(as  appears  from  the  writings  of  Aristotle,  330  B.  C,  and 
Cato,  about  200  B.  C.)  and  actually  worshiped  as  a  symbol 
of  royalty  by  the  ancient  Egyptians,  through  whose  papyri 
and  scarabs  the  honey  bee  may  be  traced  back  to  the  time  of 
Rameses  I.,  or  1400  B.  C. 

Though  its  habits  have  been  somewhat  modified  by  domesti- 
cation, the  honey  bee,  unlike  most  domesticated  animals,  is  still 
so  little  dependent  upon  man  that  it  readily  returns  to  a  wild 
life.  Under  many  distinct  races,  which  are  due  largely  to 
human  intervention.  Apis  uiclUfcra  is  widely  distributed  over 
the  earth. 

Castes. — The  species  comprises  three  kinds  of  individuals: 
queen,  drone  and  worker  (Fig.  277).     The  workers  are  fe- 

FiG.  277. 


The  honey  bee,  Apis  mcllift 
22 


,   drone;   C,  worker.     Natural   size. 


322 


ENTOMOLOGY 


males  with  an  atrophied  reproductive  system.  They  constitute 
the  vast  majority  in  any  colony  and  are  the  only  kind  that  is 
commonly  seen  out  of  doors.  Upon  the  industrious  workers 
falls  the  burden  of  the  labor;  they  build  the  comb,  nurse  the 
young,  gather  food,  clean  and  repair  the  nest,  guard  it  from 
intruders,  control  larval  development,  expel  the  drones — 
briefly,  the  workers  alone  are  responsible  for  the  general  man- 
agement of  the  community.  Though  hibernating  workers  live 
eight  or  nine  months,  the  other  workers  live  but  from  five  to 
twelve  weeks. 

The  term  queen  is,  of  course,  a  misnomer,  for  the  govern- 
ment of  the  hive  is  anything  but  monarchial.     The  chief  duties 
Pj^.    ,„g  of  the  queen,  or  mother,  are  simply  to  lay 

eggs  and  to  lead  away  a  swarm.  She  is 
able  to  deposit  as  many  as  4,000  eggs  in 
twenty-four  hours.  After  a  single  mat- 
ing, the  spermatozoa  retain  their  vitality 
in  the  spermatheca  of  the  queen  for  three 
or  four  years — the  lifetime  of  a  queen. 
The  males,  or  drones,  apart  from  their 
occasional  sexual  usefulness,  are  of  little 
or  no  service,  and  their  very  name  has 
become  an  expression  for  laziness. 

The  Comb. — Wax,  of  which  the  comb 
is   built,    is    made    from   honey   or   sugar, 
many     pounds      (twenty,      according     to 
A,  bases  of  comb  cells;  Hubcr)   of  lioucv  bciug  required  to  make 

B,  section  of  comb.    Some-  ^  ,01 

what   enlarged.— A  f  t  e  r  one  pouucl  of  wax.     The  workcrs,  gorged 

Cheshire.  .   ,  ^  ,.  ^  ,,  • 

With  nectar,  cling  to  one  another  m  a 
dense  heated  mass  until  the  white  films  of  wax  appear  under- 
neath the  abdomen  (Fig.  102)  ;  these  are  transferred  to  the 
mouth  by  means  of  the  wax-pincers  (Fig.  263,  C)  of  the  hind 
legs  and  are  masticated  with  a  fluid,  secreted  by  cephalic 
glands,  which  alters  the  chemical  composition  of  the  wax  and 
makes  it  plastic. 

The  w^orkers  now  contribute  their  wax  to  form  a  vertical, 


INTERRELATIONS    OF    INSECTS 


323 


hanging  septnm,  on  the  ()])posite  sides  of  which  they  proceed 
to  bite  ont  i)its — the  bottoms  of  the  future  ceHs — using  the 
excavated  wax  in  making  the  cell  walls.  The  bottom  of  each 
cell  consists  of  three  rhombic  plates   (b'ig.  278,  A),  and  the 


278,  B)  in  such  a  way  that  each  rhomb  serves  for  two  cells 
at  once.  Wax  is  such  a  precious  substance  that  it  is  used 
(instinctively,  however)  always  with  the  greatest  economy; 
the  cell  walls  are  scraped  to  a  thinness  of  1/280  or  even  1/400 
of  an  inch,  and  nowhere  is  more  wax  used  than  is  sufficient 
for  strength;  one  pound  of  wax  makes  from  35,000  to  50,000 
worker  cells.  The  cells,  at  first  circular  in  cross  section,  be- 
come hexagonal  from  the  mutual  interference  of  workers  on 

opposite  sides  of  the  same 

11        1         r  1  Fig.  279. 

wall ;    the    lorm,    however, 

is  by  no  means  a  regular 
hexagon  in  the  mathemat- 
ical sense,  for  it  is  difficult 
to  find  a  cell  with  errors 
of  less  than  3  or  4  degrees 
in  its  angles  (Cheshire). 
Worker  cells  are  one  fifth 
of  an  inch  in  diameter, 
wdiile  the  larger  cells,  des- 
tined for  drones  or  to  hold 
honey,  are  one  quarter  of 
an  inch  across. 

To  strengthen  the  edges 
of  cells  or  to  fill  crevices, 
the  workers  use  propolis, 
the  sticky  exudation  from 
the  buds  or  leaf  axils  of 
poplar,  fir,  horsechestnut 
or  other  trees ;  though  they  will  utilize  instead  such  artificial 
substances  as  grease,  pitch  or  varnish.  As  winter  approaches, 
the  bees  apply  the  propolis  liberally,  making  their  abode  tight 
and  comfortable. 


Comb  of  honey  bee,  showing  the  insect  in 
arious  stages.  At  the  right  are  large  queen 
ells.  — After  Renton. 


324 


ENTOMOLOGY 


Larval  Development. — When  the  brood  cells  are  ready, 
the  queen,  attended  by  workers,  lays  an  egg  in  each  cell  and 
has  no  further  concern  as  to  its  fate.  After  three  days  the  egg 
discloses  a  footless  grub  (Figs.  279,  280)  which  depends  at  first 
upon  the  milky  food  that  bathes  it  and  has  been  supplied  from 
the  mouths  of  the  worker  nurses.  Later  the  larva  is  weaned 
by  its  nurses  to  pollen,  honey  and  water.  As  the  stomach  and 
the  intestine  of  the  larva  do  not  communicate  with  each  other, 
the  excretions  of  the  larva  cannot  contaminate  the  surrounding 
nutriment,  and  they  are  retained  until  the  final  moult.  Five 
days  after  hatching,  the  larva  spins  its  cocoon,  the  workers 
having  meanwhile  covered  the  larval  cell  with  a  porous  cap 

Fig.  280. 


Honey  bee.     /,   feeding  larva;  />,   pupa;  s,  spinning  larva. — After   Cheshire. 

of  wax  and  pollen  (Fig.  280)  and  on  the  twenty-first  day  after 
the  egg  was  laid  the  winged  bee  cuts  its  way  out,  assisted  in 
this  operation  by  the  ever-attenti^'e  nurses.  Now,  after  acquir- 
ing the  use  of  its  faculties,  the  newly  emerged  bee  itself 
assumes  the  duties  of  a  nurse,  but  as  soon  as  its  cephalic  nurs- 
ing glands  are  exhausted  it  becomes  a  forager.  This  account 
applies  to  the  worker ;  the  three  kinds  of  individuals  differ  in 
respect  to  the  number  of  days  required  for  development,  as 
appears  in  the  following  table,  from  Benton  : 

Egg.  Larva.  Pupa.  Total. 

Queen,  3  S'A  7  ^S'A 

Worker,  3  5  13  21 

Drone,  3  6  15  24 

The  cells  in  which  queens  develop  (Fig.  279)  are  cjuite  dif- 
ferent from  worker  or  drone  cells,  being  much  larger,  more 


INTERRELATIONS    OF    INSECTS  3^5 

or  less  irregular  in  form,  and  vertical  instead  of  horizontal ; 
they  are  attached  usually  to  the  lower  edge  of  a  comb  or  else 
to  one  of  the  side  edges. 

Other  Facts. — The  entire  organization  of  the  lioney  bee 
has  been  profoundly  modified  with  reference  to  floral  struc- 
ture; the  life  of  the  bee  is  wrapped  up  in  that  of  the  flower. 
The  more  important  structural  adaptations  of  bees  in  relation 
to  flowers  have  been  described,  as  well  as  many  of  their  sen- 
sory peculiarities ;  there  remain  to  be  added,  however,  some 
other  items  of  interest,  chosen  from  the  many. 

A  colony  of  bees  in  good  condition  at  the  opening  of  the 
season  contains  a  laying  queen  and  some  30,000  to  40,000 
worker  bees,  or  six  to  eight  quarts  by  measurement.  Besides 
this  there  should  be  four,  five,  or  even  more  combs  fairly 
stocked  with  developing  brood,  with  a  good  supply  of  honey 
about  it.  Drones  may  also  be  present,  even  to  the  number  of 
several  hundred. 

Ordinarily  the  queen  mates  but  once,  flying  from  the  hive 
to  meet  the  drone  high  in  the  air,  when  five  to  nine  days  old 
generally.  Seminal  fluid  sufficient  to  impregnate  the  greater 
number  of  eggs  she  will  deposit  during  the  next  two  or  three 
years  (sometimes  even  four  or  five  years)  is  stored  at  the  time 
of  mating  in  a  sac — the  spennatheca,  opening  into  the  egg- 
passage.  At  the  time  the  queen  mates,  there  are  in  the  hive 
neither  eggs  nor  young  larv?e  from  which  to  rear  another 
queen ;  hence,  should  she  be  lost,  no  more  fertilized  eggs  would 
be  deposited,  and  the  old  workers  gradually  dying  ofif  wdthout 
being  replaced  by  young  ones,  the  colony  would  become  extinct 
in  the  course  of  a  few  months  at  most,  or  meet  a  speedier  fate 
through  intruders,  such  as  wax-moth  larvae,  robber  bees, 
wasps,  etc.,  which  its  weakness  would  prevent  its  repelling 
longer;  or  cold  is  very  likely  to  finish  such  a  decimated  colony, 
especially  as  the  bees,  because  queenless,  are  uneasy  and  do 
not  cluster  compactly. 

The  liquid  secreted  in  the  nectaries  of  flowers  is  usually  quite 
thin,  containing,  when  just  gathered,  a  large  percentage  of 


3^6  ENTOMOLOGY 

water.  Bees  suck  or  lap  it  up  from  such  flowers  as  they  can 
reach  with  their  flexible,  sucking  tongue,  0.25  to  0.28  inch 
long.  This  nectar  is  taken  into  the  lioncy  sac,  located  in  the 
abdomen,  for  transportation  to  the  hive.  Besides  being  thin, 
the  nectar  has  at  first  a  raw,  rank  taste,  generally  the  flavor 
and  odor  peculiar  to  the  plant  from  which  gathered,  and  these 
are  frequently  far  from  agreeable.  To  make  from  this  raw- 
product  the  healthful  and  delicious  table  luxury  which  honey 
constitutes — "  fit  food  for  the  gods  " — is  another  of  the  func- 
tions peculiar  to  the  worker  bee.  The  first  step  is  the  station- 
ing of  workers  in  lines  near  the  hive  entrances.  These,  by 
incessant  buzzing  of  their  wings,  drive  currents  of  air  into  and 
out  of  the  hive  and  over  the  comb  surfaces.  If  the  hand  be 
held  before  the  entrance  at  such  a  time  a  strong  current  of 
warm  air  may  be  felt  coming  out.  The  loud  buzzing  heard  at 
night  during  the  summer  time  is  due  to  the  wings  of  workers 
engaged  chiefly  in  ripening  nectar.  Instead  of  being  at  rest, 
as  many  suppose,  the  busy  workers  are  caring  for  the  last- 
gathered  lot  of  nectar  and  making  room  for  further  accessions. 
This  may  go  on  far  into  the  night,  or  even  all  night,  to  a 
greater  or  less  extent,  the  loudness  and  activity  being  propor- 
tionate to  the  amount  and  thinness  of  the  liquid.  Frequently 
^.he  ripening  honey  is  removed  from  one  set  of  cells  and  placed 
in  others.  This  may  be  to  gain  the  use  of  certain  combs  for 
the  queen,  or  possibly  it  is  merely  incidental  to  the  manipula- 
tion the  bees  wish  to  give  it.  When,  finally,  the  process  has 
been  completed,  it  is  found  that  the  water  content  has  usually 
been  reduced  to  10  or  12  per  cent.,  and  that  the  disagreeable 
odors  and  flavors,  probably  due  to  volatile  oils,  have  also  been 
driven  off  in  a  great  measure,  if  not  wholly,  by  the  heat  of 
the  hive,  largely  generated  by  the  bees.  During  the  manipu- 
lation an  antiseptic  (formic  acid)  secreted  by  glands  in  the 
head  of  the  bee,  and  possibly  other  glandular  secretions  as  well 
have  been  added.  The  finished  product  is  stored  in  waxen 
cells  above  and  around  the  brood  nest  and  the  main  cluster  of 
bees,  as  far  from  the  entrance  as  it  can  be  and  still  be  near 


INTERRELATIONS    OF    INSECTS  327 

to  the  bro(Ml  and  l)ees.  Tlie  work  of  scalini;-  with  waxen  caj^s 
then  g-ocs  forward  rapidl)-.  the  C(^\crino-  l)ein_g-  more  or  less 
porous.  Eacli  kind  of  lioney  has  its  distinctive  flavor  and 
aroma,  derived,  as  already  indicated,  mainly  from  the  particu- 
lar blossoms  by  which  it  was  secreted,  but  modified  and  soft- 
ened by  the  manipulaticMi  given  it  in  the  hives.  The  last  three 
paragraphs  are  taken  from  Benton's  useful  manual. 

The  phenomenon  of  "  swarming  "  results  from  the  tremen- 
dous repro(lucti\'e  capacity  of  the  queen,  though  it  is  immedi- 
ately an  instance  of  posit k'c  pliototropisui,  as  Kellogg  has 
shown.  Accompanied  l)y  most  of  the  workers,  the  old  cjueen 
abandons  the  hive  to  establish  a  new  colony.  The  workers 
that  remain  behind  have  provided  against  this  contingency, 
however,  and  the  departed  queen  is  soon,  if  not  already,  re- 
placed by  a  new  one. 

Determination  of  Caste. — The  difference  lietween  queen 
and  worker  depends  solely  upon  nutrition,  both  forms  being 
deri\'ed  from  precisely  the  same  kind  of  egg.  To  produce  a 
queen,  a  large  cell  of  special  form  is  constructed,  and  its  occu- 
pant, instead  of  being  weaned,  is  fed  almost  entirely  upon  the 
highly  nutritious  secretion  which  worker  grubs  receive  only  at 
first  and  in  limited  quantity.  This  nitrogenous  food,  the 
product  of  cephalic  glands,  develops  the  reproductive  system 
in  proportion  to  the  amount  received.  Drone  larvse  get  much 
of  it,  though  not  so  much  as  queens,  while  an  occasional  excess 
of  this  "  royal  jelly  "  is  believed  to  account  for  the  abnormal 
appearance  of  fertile  workers. 

Parthenogenesis,  or  reproduction  without  fertilization,  is 
kno\vn  to  occur  in  the  bee,  as  well  as  in  various  other  insects. 
The  always  unfertilized  eggs  of  \vorkers  produce  invariably 
drones,  as  do  also  unfertilized  eggs  of  the  queen.  Probably 
the  cjueen  cannot  control  the  sex  of  her  eg'gs,  as  she  has  long 
been  supposed  to  do,  for  Dickel  has  recently  found,  among 
other  revolutionary'  facts,  that  all  the  eggs  of  the  normal 
mother  bee  are  fertilized. 


326  entomology 

Bumble  Bees 
Familiar  as  the  buml)le  bees  are,  their  habits  are  but  imper- 
fectly known.  The  queen  hibernates  and  in  spring-  starts  a 
colony,  utilizing  frequently  for  this  purpose  the  deserted  nest 
of  a  field  mouse  or  sometimes  the  burrow  of  a  mole  or  gopher. 
The  queen  lays  her  eggs  in  a  small  mass  of  pollen  mixed  with 
nectar  (Putnam).  The  larvje  eat  out  cavities  in  the  mass  of 
food  and  when  full  grown  spin  silken  cocoons,  from  which  the 
imago  cuts  its  way  out;  the  empty  cocoon  being  subsequently 
used  as  a  receptacle  for  honey.  At  first  only  workers  are 
produced  and  they  at  once  relieve  the  queen  of  the  duties  of 
collecting  nectar  and  pollen,  caring  for  the  young,  etc.  The 
workers  are  of  different  sizes,  the  smaller  ones  being  nurses 
or  builders  and  the  larger  ones  foragers — the  kind  commonly 
seen  out  of  doors.  In  the  latter  part  of  summer  both  males 
and  females  are  produced,  but  when  severe  frost  arrives,  the 
old  queen,  the  workers  and  the  males  succumb,  leaving  only 
the  young  queens  to  survive  the  winter. 

SocL\L  Wasps 

The  Social  Wasps  constitute  the  family  Vespid?e,  of  which 
we  have  three  genera,  namely,  Vcspa,  Polistcs  and  Polybia, 
the  last  genus  being  represented  by  a  single  Californian  species. 

Vespa. — Some  species  of  J^cspa,  as  ]\  inaculata,  make  a 
nest  which  consists  of  several  tiers  of  cells  protected  by  an 
envelope  (Fig.  281),  attaching  the  nest  frequently  to  a  tree; 
other  species,  as  gcniianica  and  vulgaris,  make  a  nest  under- 
ground. The  paper  of  which  the  nests  are  composed  is  manu- 
factured from  weather-worn  shreds  of  wood,  which  are  torn 
off  by  the  mandibles  and  then  masticated  with  a  secreted  fluid 
which  cements  the  paper  and  makes  it  waterproof. 

A  solitary  queen  founds  the  colony  in  spring;  she  starts  the 
nest,  lays  eggs,  feeds  the  young  and  brings  forth  the  first 
workers;  these  then  relieve  her — continue  the  building  opera- 
tions, collect  food,  nurse  the  young,  in  short,  assume  the  bur- 
den of  the  labor.      In  the  latter  part  of  summer,  fertile  males 


INTERRELATIONS    OF    INSECTS 


329 


and  females  ap])ear  and  ])airin£^-  occnrs.  1dinng-li  tlie  statement 
has  often  l)een  made  that  only  the  )-inin_i;-  c|neens  sin'\-i\-e  the 
winter,  there  is  some  reason  to  belie\'e  that  not  only  the  queens 
but  also  males  and  workers  may  hibernate  successfully  in  the 
nest. 

The  ]ar\-;c  are  fed  at  hrst,  b}'  rei;in\^itati()n,  upon  the  sugary 
nectar  of  tlowers  and  the  juices  of  fruits,  and  later  u])on  more 

Fig.  281. 


Nest  of  wasp,    J'espa   maculata.     A,   outer   aspect;    B.   with   envelope   cut   away   to   show 
combs.     Greatly    reduced. 

substantial  food,  such  as  the  softer  parts  of  caterpillars,  flies. 
bees,  etc.,  reduced  to  a  pulp  by  mastication;  occasionally  wasps 
steal  honey  from  bees. 

The  workers,  as  is  usual  among  social  Hymenoptera,  are 
modified  females,  incapable  of  reproduction  as  a  rule,  though 
the  distinction  between  worker  and  queen  is  not  nearly  so  sharp 
among  wasps  as  it  is  among  bees.  Worker  eggs  are  said  to 
be  parthenogenetic  and  to  produce  only  males.  The  males, 
unlike  those  of  the  honey  bee,  are  active  laborers  in  the  colony. 
In  the  tropics  there  are  wasps  that  form  permanent  colonies, 
store  hone}-  and  swarm,  after  the  fashion  of  honey  bees. 

Polistes. — The  preceding  description  of  Vcspa  applies 
equally  well  to  our  several  species  of  Polistes,  except  that  the 


330  ENTOMOLOGY 

nest  of  Polistcs  is  a  single  comb  hanging  by  a  pedicel  and  with- 
ont  a  protecting  envelope.  Miss  Enteman,  who  has  carefnlly 
studied  the  habits  of  Polistcs,  finds  that  the  larva  spins  a  lin- 
ing as  well  as  a  cap  for  its  cell,  by  means  of  a  fluid  from  the 
mouth,  and  that  the  adults  emerge  after  a  pupal  period  of  three 
weeks,  males  and  females  appearing  (in  the  vicinity  of  Chi- 
cago) in  the  latter  part  of  August  and  early  in  September. 

Ants 

The  habits  of  ants  have  engaged  the  serious  attention  of 
some  of  the  most  sagacious  students  of  the  phenomena  of  life. 
Any  species  of  ant  presents  innumerable  problems  to  the 
thoughtful  investigator  and  no  less  than  two  thousand  species 
of  ants  are  already  known. 

A  large  part  of  our  knowledge  of  the  habits  of  these  remar- 
kable insects  has  been  obtained  by  the  use  of  artificial  formi- 
caries, which  are  easily  constructed  and  have  yielded  important 
results  in  the  hands  of  Lubbock,  Forel,  Janet,  Wasmann, 
Fielde,  Wheeler  and  other  well-known  students  of  ants. 

Castes. — In  a  colony  of  ants  three  kinds  of  individuals  are 
produced  as  a  rule :  males,  females  and  workers,  the  last  being 
sexually  imperfect  females. 

The  males  and  females  swarm  into  the  air  for  a  nuptial 
flight,  after  which  the  males  die,  but  the  females  shed  their 
wings  and  enter  upon  a  new  and  prolific  existence,  which  may 
last  for  many  years;  a  queen  of  Lasiits  iiiger  was  kept  alive 
by  Lubbock  for  nine  years,  and  one  of  Formica  fiisca,  fifteen 
years,  and  then  its  death  was  due  to  an  accident. 

The  workers  live  from  one  to  seven  years,  according  to  the 
same  authority.  They  constitute  the  vast  majority  in  any 
colony  and  are  the  familiar  forms  that  so  often  command  at- 
tention by  their  industry  and  pertinacity.  In  some  species 
certain  of  the  workers  are  known  as  soldiers;  these  may  be 
recognized  l)y  their  larger  heads  and  mandibles. 

Polymorphism. — Ants  and  termites  surpass  all  other  in- 
sects in  respect  to  the  number  of  forms  under  which  a  single 


INTERRELATIONS    OF    INSECTS  331 

species  may  occur.  In  some  species  of  ants  several  types  of 
workers  exist ;  these  are  disting-uished  by  structural  peculiari- 
ties of  one  kind  or  another,  which  possibly  indicate  special 
functions,  for  the  most  i)art  as  yet  unascertained.  Further- 
more, the  sexual  indixiduals  are  not  necessarily  wing-ed  ;  some 
or  all  of  them  mav  be  wingless,  especially  the  females.  These 
wing-less  males  and  females  are  termed  crgatoid,  on  account 
of  their  reseml)lance  to  workers. 

As  to  how  these  various  forms  are  produced,  very  little  is 
known.  Proljably.  as  among  bees,  workers  and  queens  are 
produced  from  the  same  kind  of  eggs,  which  have  been  ferti- 
lized, and  the  differences  between  worker  and  queen  and  be- 
tween workers  themselves  may  be  due  to  the  ([uality  and  quan- 
tity of  the  food  that  is  supplied  to  the  larvae  by  their  nurses. 
As  in  bees,  the  parthenogenetic  eggs  laid  by  abnormal  workers 
may  produce  males,  as  Forel,  Lubbock  and  Miss  Fielde  have 
found ;  or  they  may  produce  normal  workers,  as  Reichenbach 
and  Mrs.  .V.  B.  Comstock  have  found  to  be  the  case  in  Lasius 
iiigcr.  Wheeler  points  out  the  possibility  of  the  inheritance 
of  worker  characters  through  the  male  offspring  of  workers. 

Larvae. — The  numerous  eggs  laid  by  one  or  more  queens 
are  taken  in  charge  by  the  young  workers,  through  ^^■hose 
assiduous  care  the  helpless  larvae  are  carried  to  maturity.  The 
nurses  feed  the  larvc'e  from  their  own  mouths,  clean  the  larvcC, 
and  carry  them  from  one  place  to  another  in  order  to  secure 
the  optimum  conditions  of  temperature,  moisture,  etc.  When 
a  nest  is  broken  open,  the  workers  seize  the  larv?e  and  pupie 
and  hurry  into  some  dark  place.  The  pupa  is  either  naked 
or  else  enclosed  in  a  cocoon,  spun  by  the  larva. 

Nests. — The  species  of  the  tropical  genus  Ecitoii  do  not 
make  nests  but  occupy  temporarily  any  suitable  retreat  which 
they  may  happen  to  find  in  the  course 
Ants  in  g-eneral  know  how  to  utilize  al 
ties  as  nests ;  they  make  use  of  crevices  in  rocks  and  under 
stones  or  bark,  the  holes  made  by  bark-beetles,  hollow  stems 
or  roots,  plant-galls,  fruits,  etc.  The  extraordinary  '*  ant- 
plants  "  have  already  received  special  consideration. 


332  ENTOMOLOGY 

Very  many  ants  excavate  their  nests  in  the  ground ;  after 
a  rain  these  ants  are  especially  industrious  in  the  improvement 
of  the  nest,  pressing  the  wet  earth  into  the  walls  of  the  gal- 
leries and  adding  probably  a  secreted  fluid  which  acts  as  a 
cement ;  stones  and  sticks  are  often  worked  into  the  walls  of 
a  nest  and  the  mounds  of  ants  are  frequently  fashioned  about 
blades  of  grass  or  growing  herbage  of  whatever  kind.  The 
subterranean  galleries  are  often  complex  labyrinths ;  frequenth^ 
there  are  long  underground  passages  extending  out  in  all  direc- 
tions, sometimes  to  aphid-infested  roots  of  plants  or,  as  in  the 
case  of  the  leaf-cutting  ants  of  the  tropics,  to  trees  which  are 
destined  to  be  attacked ;  special  chambers  are  set  apart  for  the 
storage  of  food  and  others  for  eggs,  larvse  or  pupae. 

Often  a  nest  is  excavated  under  a  stone.  As  Forel  ob- 
serves, the  stone  warms  speedily  under  the  rays  of  the  sun, 
and  in  damp  or  cool  weather  the  ants  are  always  in  the  highest 
story  of  the  nest  as  soon  as  the  sun's  warmth  begins  to  pene- 
trate the  soil,  while  they  go  below  as  soon  as  the  sun  disap- 
pears or  when  its  heat  becomes  too  strong.  They  select  stones 
that  are  neither  too  large  nor  too  small  to  regulate  the  tem- 
perature well,  while  other  ants  attain  the  same  object  by  mak- 
ing the  nest  under  sheltering  herbage  or  by  making  a  mound 
with  a  hard  cemented  roof. 

The  well-known  ant-hills  may  consist  simply  of  excavated 
particles  of  soil  or  else,  as  in  the  huge  mounds  of  Fonnica 
csscctoidcs,  may  contain  labyrinthine  passages  in  addition  to 
those  underground.  The  mounds  of  this  species  are  elaborate 
structures  which  may  last  a  man's  lifetime  at  least.  F.  cxscc- 
foidcs  is  accustomed  to  form  new  colonies  in  connection  with 
the  parent  nest;  McCook  found  in  the  Alleghanies  no  less  than 
1, 600  nests,  forming  a  single  enormous  community  with  hun- 
dreds of  millions  of  inhabitants,  hostile  to  all  other  colonies  of 
ants,  even  those  of  the  same  species.  This  ant  covers  its 
mound  with  twig's,  dead  leaves,  grass  and  all  sorts  of  foreign 
material,  and  is  said  to  close  the  exits  of  the  nest  with  bits  of 
wood  at  night  and  in  rainy  weather,  removing  them  in  the 
morning  or  when  the  weather  becomes  favorable. 


INTERRELATIONS    OF    INSECTS  T,^^ 

As  Forel  says  [translation]  :  "  The  chief  feature  (^f  ant 
architecture,  in  contrachstinction  to  tliat  of  the  l)ees  and  the 
\vasi)s.  is  its  irrei^'ularity  and  want  of  uniforniit\- — tliat  is  to 
say.  its  adaptal)ihty.  or  the  capacity  of  making-  all  the  sur- 
roundings and  incidents  subserve  the  purjiose  of  attaining  the 
greatest  possil)le  economy  of  space  and  time  and  the  greatest 
])(^ssil)le  comfort.  For  instance,  the  same  species  will  live  in 
the  Alps  under  stones  which  absorb  the  rays  of  the  sun;  in  a 
forest  it  will  live  in  warm,  decayed  trunks  of  trees;  in  a  rich 
mead(^w  it  will  live  in  high,  conical  mounds  of  earth."  Some 
species  construct  peculiar  pasteboard  nests,  as  Lasiiis  ftilii^iiio- 
sits  of  Europe  and  tropical  species  of  Crciiiastogastcr;  and 
others  spin  silk  to  fasten  leaves  together,  as  Polyrhachis  of 
India  and  Qicophylla  of  tropical  Asia  and  tropical  Africa,  the 
silk  being  probably  a  salivary  secretion,  according  to  Forel. 

Habits  in  General. — The  habits  of  ants  are  an  inexhaustible 
and  ever-fascinating  subject  of  study  to  the  naturalist,  and 
well  repay  the  most  critical  observation.  While  each  species 
has  its  characteristic  habits,  ants  in  general  have  many  customs 
in  common. 

Thus  ants  of  one  colony  exhibit,  as  a  rule,  a  pronounced 
hostility  toward  ants  of  any  other  colony,  even  one  of  the  same 
species,  but  recognize  and  spare  members  of  their  own  colony, 
even  after  many  months  of  separation  and  though  the  colony 
may  number  half  a  million  individuals.  This  recognition  is 
effected  by  means  of  an  odor,  distinctive  of  the  colony  and  ap- 
parently inheritable.  When  an  ant  is  washed  and  then  restored 
to  its  fellows,  it  is  treated  at  first  as  an  intruder  and  may  even  be 
killed.  The  same  is  true  when  the  ant  has  been  smeared  with 
juices  from  the  bodies  of  alien  ants.  According  to  Miss 
Fielde,  workers  of  colony  A,  smeared  with  the  juices  from 
crushed  ants  of  colony  B  and  then  placed  in  colony  B  are 
received  amicably,  but  at  once  set  about  to  destroy  their  hosts, 
like  "  wolves  in  sheep's  clothing."  These  statements  apply 
only  to  workers,  however,  for  alien  larvae  and  pup?e  are  fre- 
quently captured  and  reared  by  ants,  and  Miss  Fielde  states 


334  ENTOMOLOGY 

that  king's  of  one  colony  of  Sfciiamiiia  when  introduced  into 
anotlier  colony  are  even  cordially  received. 

Some  of  the  most  careful  students  of  the  habits  of  ants  agree 
that  these  insects  can  communicate  with  one  another.  An  ant 
discovers  a  supply  of  food,  returns  toward  the  nest,  meets  a 
fellow  worker,  the  two  stroke  antenucne  and  then  both  start 
back  to  the  food ;  before  long  other  members  of  the  colony 
swarm  to  the  prize.  It  has  been  thought  that  the  odor  of  the 
food  or  some  other  odor,  left  by  the  first  ant,  serves  as  a  trail 
for  the  other  ants  to  follow.  Bethe,  indeed,  infers  from  his 
experiments  that  this  phenomenon  is  purely  mechanical  and 
involves  no  psychical  qualities  on  the  part  of  the  ants.  His 
Dwn  experiments,  however,  show  that  one  ant  can  inform  an- 
other by  means  of  an  odor  as  to  the  whereabouts  of  food — 
which  is  certainly  one  form  of  communication. 

Ants  avoid  sunlight  as  a  rule  but  prefer  rays  of  lower  re- 
frangibility  to  those  of  higher.  Upon  exposing  ants  to  the 
colors  of  the  spectrum,  as  transmitted  through  glasses  of  dif- 
ferent colors,  Lubbock  found  that  they  congregated  in  greatest 
numbers  under  the  red  glass  and  that  the  numbers  diminished 
regularly  from  the  red  to  the  violet  end  of  the  spectrum,  there 
being  very  few  individuals  under  the  violet  glass. 

Miss  Fielde,  experimenting  with  cjueens,  workers  and  young 
of  Stcnamma  fulvum  picciiui  in  an  artificial  nest,  covered  half 
the  nest  with  orange  glass  and  half  with  violet.  '*  The  ants  re- 
moved hastily  from  under  the  violet  as  often  as  an  interchange 
of  the  panes  was  made,  once  or  twice  a  day,  for  about  twenty 
days.  Thereafter  they  became  indifi^erent  to  the  violet  rays." 
"  The  plasticity  of  the  ants  is  remarkably  shown  in  their  grad- 
ually learning  to  stay  where  they  were  never  disturbed  by  me, 
under  rays  from  which  their  instincts  at  first  withdrew  them." 

Ants  are  sensitive  not  only  to  the  different  colors  of  the 
spectrum  but  also  to  the  ultra-violet  rays,  which  produce  no 
appreciable  effect  on  the  human  retina  (though  they  induce 
chemical  changes).  If  obliged  to  choose  between  the  two.  ants 
prefer  violet  to  ultra-violet  rays,  as  Lubbock  found.     If,  how- 


INTERRELATIONS    OF    INSECTS  335 

ever,  the  ultra-violet  rays  are  intercepted.  l)y  means  of  a  screen 
of  sulphate  of  (|uinine  or  l)isuli)hi(le  of  carbon,  the  ants  then 
collect  under  the  screen  in  preference  to  under  the  \'iolet  rays. 

r^'om  lack  of  experience  we  can  form  no  ade(|uate  idea  as 
to  the  range  of  sensation  in  ants  or  other  insects.  Ants  can 
taste  substances  that  we  cannot,  and  vice  versa.  They  show 
no  response  to  sounds  of  human  contrivance,  yet  many  of  them 
possess  stridulating  organs  and  organs  that  are  doubtless  audi- 
tor}-; whence  it  may  be  inferred  that  ants  can  communicate 
with  one  another  by  means  of  sounds.  In  rare  instances  the 
stridulation  of  an  ant  can  impress  the  human  ear,  as  in  a  spe- 
cies of  At  fa  mentioned  by  Sharp. 

Experiments  show  that  ants,  as  well  as  bees  and  wasps,  find 
their  way  back  to  the  nest,  not  by  a  mysterious  "  sense  of 
direction,"  but  by  remembering  the  details  of  the  surroundings, 
and  in  the  case  of  ants,  by  means  of  an  odor  left  along  the 
trail. 

In  studying  the  habits  of  ants,  the  greatest  care  must  be 
exercised  in  order  to  discriminate  between  actions  that  may 
be  regarded  as  purely  instinctive  and  those  that  may  indicate 
some  degree  of  intelligence.  If  any  insects  show  sig'ns  of  in- 
telligence, the  social  Hymenoptera  do  so ;  but  in  the  study  of 
this  recondite  subject,  false  conclusions  can  be  avoided  only 
l)y  observation  and  experiment  of  the  most  critical  kind. 

Hunting  Ants. — Some  ants,  as  Formica  fusca,  live  by  the 
chase,  hunting  their  prey  singly.  The  African  "  driver  ants  " 
(Anoinnia  airois),  although  blind,  hunt  in  immense  droves, 
consuming  all  the  animal  refuse  in  their  way,  devouring  all  the 
insects  they  meet,  and  not  hesitating  to  attack  all  kinds  of  ver- 
tebrates ;  these  ants  ransack  houses  from  time  to  time  and 
clear  them  of  all  vermin,  though  they  themselves  are  a  great 
nuisance  to  the  householder.  The  Brazilian  species  of  Ecitou 
(Fig.  283,  B,  C)  have  similar  habits  and  are  likewise  blind,  or 
else  have  but  a  single  lens  on  each  side  of  the  head.  These  in- 
sects hunt  in  armies  of  hundreds  of  thousands,  to  the  terror  of 
everv  animate  thing  that  thev  come  across.     Thev  have  no 


SS^  ENTOMOLOGY 

permanent  abode,  but  now  and  then  appropriate  some  conveni- 
ent hole  for  the  purpose  of  raising  a  new  brood  of  marauders. 

Slave-making  Ants. — It  is  a  fact  that  some  ants  make 
sla^'es  of  other  species.  Formica  saiiguiiica,  for  example,  will 
attack  a  colony  of  Formica  fiisca,  kill  its  active  members  in 
spite  of  their  determined  resistance,  kidnap  the  larv?e  and  pupae 
and  carry  them  home,  where  the  captives  receive  every  care, 
and  at  length,  as  imagines,  serve  their  masters  as  faithfully  as 
they  would  serve  their  own  species.  In  the  x-\lleghanies,  ac- 
cording to  McCook,  colonies  of  F.  fusca  occur  where  there  are 
no  "  red  ants  "  (F.  sangiiinca),  but  are  hard  to  find  where  the 
enslaving  species  occurs. 

Although  F.  saiigiiiiica  can  exist  very  well  without  slaves. 
Polycrgus  rufcscciis,  of  Europe,  is  notoriously  dependent  upon 
their  services,  it  being  doubtful  whether  it  is  capable  of  feed- 
ing itself.  This  species  is  powerful  as  a  warrior,  but  its  man- 
dibles are  of  little  use,  except  to  pierce  the  head  of  an  adver- 
sary. Sfroiigyloiiotiis  is  still  more  helpless,  while  Ancrgatcs 
(also  of  Europe)  is  said  to  depend  absolutely  upon  its  slaves. 

Polycrgus  litcidiis  occurs  in  the  Alleghanies,  where  the  col- 
onies of  this  species,  according  to  McCook,  contain  large  num- 
bers of  the  workers  of  Formica  schaiifussi.  The  masters  are 
good  fighters  but  do  no  other  work,  and  have  not  been  seen  to 
feed  themselves,  though  they  may  often  be  seen  feeding  from 
the  mouths  of  their  slaves. 

Honey  Ants. — Among  ants  in  general,  the  workers  that 
stay  in  the  nest  receive  food  from  the  mouths  of  the  foragers 
— a  custom  which  has  led  to  the  extraordinary  conditions 
found  in  the  "  honey  ants,"  in  which  certain  of  the  workers 
sacrifice  their  own  activity  in  order  to  act  as  living  reservoirs 
of  food  for  the  benefit  of  the  other  members  of  the  colony. 
This  remarkable  habit  has  arisen  independently,  in  different 
genera  of  ants,  in  North  America,  Australia  and  South  Africa, 
as  Lubbock  observes. 

The  honey  ant  whose  habits  are  best  known,  through  the 
studies  of  McCook  and  others,  is  Myrmccocystus  mcUigcr,  of 


INTERRELATIONS    OF    INSECTS 


337 


Mexico,  New  Mexico  and  southern  Colorado.  In  this  species 
some  of  the  workers  hang  skig-gishly  from  the  roof  of  their 
Httle  dome-hke  chamher,  several  inches  underground,  and  act 
as  permanent  receptacles  for  the  so-called  honey,  which  is  a 
transparent  sugary  exudation  from  certain  oak-galls ;  it  is  gath- 
ered at  night  by  the  foraging  workers  and  regurgitated  to  the 

Fig.  282. 


Honey    ants,    Myntiecocystus    mclligcr,   clinging   to    the    roof   of    tht^ir    chamber, 
natural    size. — After   McCook. 


mouths  of  the  "  honey-bearers,"  whose  crops  at  length  become 
distended  with  honey  to  such  an  extent  that  the  insects  (Fig. 
282)  look  like  so  many  little  translucent  grapes  or  good-sized 
currants.  This  stored  food  is  in  all  probability  drawn  upon 
by  the  other  ants  when  necessary. 

Leaf-cutting  Ants. — The  most  dangerous  foes  to  vegeta- 
tion in  tropical  America  are  the  several  species  of  Atta  (CEco- 
doiiia,  Fig.  283,  A).  Living  in  enormous  colonies  and  capable 
of  stripping  a  tree  of  its  leaves  in  a  few  hours,  these  formida- 
ble ants  are  the  despair  of  the  planter;  where  they  are  abun- 
dant it  becomes  impossible  to  grow  the  orange,  coffee,  mango 
and  many  other  plants.  These  ants  dig  an  extensive  under- 
ground nest,  piling  the  excavated  earth  into  a  mound,  some- 
23 


338 


ENTOMOLOGY 


times  thirty  or  forty  feet  in  diameter,  and  making  paths  in 
various  directions  from  the  nest  for  access  to  the  plants  of  the 


Fig. 


A,    leaf-cutting    ant,    Atfa    ccphalotcs.     B,    wandering    ant,    Eciton    drcfanophorum ;    C, 
Eciton  omnivoriun.     Natural  size. — After   Shipley. 


Fig.  284. 


vicinity ;  Belt  often  found  these  ants  at  work  half  a  mile  from 
their  nest;  they  attack  flowers,  fruits  and  seeds,  but  chiefly 
leaves.  Each  ant,  by  laboring 
four  or  fi\-e  minutes,   bites   out  a 


a  leaf  (Fig.  284)  and  carries  it 
home,  or  else  drops  it  for  another 
worker  to  carry ;  and  two  strings 
of  ants  may  be  seen,  one  carry- 
ing their  leafy  burdens  toward  the 
nest,  the  other  returning  for  more 
plunder. 

The  use  made  of  these  leaves 
has  been  the  subject  of  much  dis- 
cussion. Belt  found  the  true  ex- 
planation, but  it  remained  for 
Moller  to  investigate  the  subject 
so  thoroughly  as  to  leave  no  room 
for  doubt.  The  ants  grow  a  fun- 
gus upon  these  leaves  and  use  it 
as  food.  The  bits  of  leaves  are 
kneaded  into  a  pulpy,  spongy 
mass,  upon  which  the  fungus  at 
length     appears.      The     food     for 


A,  B,  cuts  made  in  Ciiphea 
leaves  in  four  or  five  minutes  by 
Atta  discigera;  natural  size.  C, 
Atta  discigera  transporting  severed 
fragments  of  leaves;  reduced. — 
After  Moller. 


INTERRELATIONS    OF    INSECTS 


339 


Fk;.  28; 


the  sake  n{  which  the  ants  carry  on  their  complex  o])er- 
ations  consists  of  the  knobbed  ends  of  fnni^ns  threads 
(Fig.  285),  and  these  bodies,  rich  in  fluid,  form  the  most 
important,  if  not  the  sole  food  of  the  leaf-cnttini^-  ants,  fjy 
assiduously  wcedins;-  out  all  foreig-n  organisms  the  ants  ob- 
tain a  pure  culture  of  the  fungus,  and  by  pruning  the  fungus 
the}'  keep  it  in  the  N'egeta- 
tive  condition  and  pre\-ent 
its  fructification:  under 
exceptional  circumstances, 
however,  the  fungus  de\-el- 
oi)s  aerial  organs  of  fructi- 
fication of  the  agaricine 
type,  but  this  species  (Ro- 
£ifcs  gongylophova )  has 
never  been  found  outside 
of  ants'  nests.  The  pecu- 
har  clubbed  threads  were 
produced  by  Moller  in  arti- 
ficial cultures  and  are  not 
spores,  but  products  of  cul- 
ti^'ation.  Other  ants  are  known  to  cultivate  other  kinds  of 
fungi  for  similar  purposes. 

McCook  has  found  a  leaf-cutting  ant  {Atta  fcrvcns)  in 
Texas,  and  mentions  that  it  cuts  circular  pieces  out  of  leaves 
of  chietiy  the  live-oak,  these  being  (h-opped  to  the  ground  and 
taken  to  the  nest  by  another  set  of  workers.  He  records  an 
underground  tunnel  of  Atta  fcrvens  which  extended  448  feet 
from  the  nest  and  then  opened  into  a  path  185  feet  in  length; 
the  tunnel  w^as  18  inches  below  the  surface  on  an  average, 
though  occasionally  as  deep  as  6  feet,  and  the  entire  route  led 
with  remarkable  precision  to  a  tree  which  was  being  defoliated. 

The  same  observer  has  given  also  a  brief  account  of  a  leaf- 
cutting  ant  that  lives  in  New  Jersey.  This  species  (Atta  scp- 
tcntrionalis)  cuts  the  needle-like  leaves  of  seedling  pines  into 
httle  pieces,  which  are  carried  to  the  nest.     Two  columns  of 


Fungus  clumiis  {Rocitcs  gongylof'lwra) 
cultivated  by  ants  of  the  genus  Atta. 
Greatly   magnified. — After   Moller. 


340  ENTOMOLOGY 

workers  may  be  seen,  one  composed  of  individuals  returning 
to  the  nest,  each  with  a  piece  of  a  pine  needle,  the  other  of 
outgoing  workers.  The  nest  is  a  simple  structure,  extending 
some  seven  inches  underground  and  ending  in  a  chamber  in 
which  are  several  small  pulpy  balls,  consisting  probably  of 
masticated  leaves.  Further  studies  upon  our  own  leaf-cutting 
ants,  modeled  after  the  admirable  studies  of  Moller,  are  much 
to  be  desired. 

Harvesting  Ants. — Lubbock  observes  that  some  ants  col- 
lect the  seeds  of  violets  and  grasses  and  preserve  them  care- 
fully for  some  purpose  as  yet  unknown.  From  such  a  begin- 
ning as  this  may  have  arisen  the  extraordinary  habits  of  the 
agricultural,  or  harvesting,  ants,  of  which  some  twenty  species 
are  known  from  various  parts  of  the  world. 

The  Texas  species  Pogonouiyrmcx  harhafus,  studied  by 
Lincecum  and  by  McCook,  clears  away  the  herbage  around  its 
nest  (even  plants  several  feet  high  and  as  thick  as  a  man's 
thumb)  and  levels  the  ground,  forming  a  disk  often  lo  or  12 
and  sometimes  15  to  20  feet  in  diameter,  from  which  radiating 
paths  are  made,  from  60  to  300  feet  in  length.  The  ants  go 
back  and  forth  along  these  roads,  carrying  to  the  nest  seeds 
which  they  have  collected  from  the  ground  or  else  have  cut 
from  plants ;  these  seeds  are  stored  in  "  granaries  "  several  feet 
underground  and  are  eventually  used  as  food.  The  ants  pre- 
fer the  seeds  of  a  grass,  Arisfida  oUgantha,  but  the  oft-repeated 
statement  that  they  sow  the  seeds  of  this  "  ant-rice,"  guard  it 
and  weed  it,  is  denied  by  Wheeler. 

Notwithstanding  the  elaborate  studies  of  McCook  upon  this 
subject,  there  still  remain  not  a  few  essential  questions  to  be 
answered. 

Myrmecophilism. — To  add  to  the  complexity  of  ant-life, 
the  nests  of  ants,  when  at  all  extensive,  are  frequented  by  a 
great  variety  of  other  arthropods,  which  on  account  of  their 
association  with  ants  are  termed  inyniiccophilcs.  Most  of 
these  are  insects,  of  which  Wasmann  has  catalogued  1,200 
species,   but   not   a    few   are   spiders,   mites,   crustaceans,   etc. 


INTERRELATIONS    OF    INSECTS  341 

Thoug-h  the  di\'erse  relations  l:>et\veen  myrmecophiles  and  ants 
are  but  partially  understood,  these  aliens  may  for  convenience 
be  considered  under  f\\e  ""roups  :  captii'cs,  i:^!icsts.  Z'isitors,  iji- 
trudcrs  and  parasites. 

Captives. —  l^esides  ens]a\ing-  other  species,  as  already  men- 
tioned, ants  make  use  of  aphids  and  some  coccids  for  the  sake 
of  their  palatable  products.  The  attendance  of  ants  upon  col- 
onies of  plant  lice  is  a  common  occurrence  and  one  that  repays 
careful  observation.  With  the  aid  of  a  hand-lens,  one  may 
see  the  ants  hastening"  about  among"  the  plant  lice  and  patting" 
them  nervously  with  the  antenna.^  until  at  length  some  aphid 
responds  by  emitting"  from  the  end  of  the  abdomen  a  g^listening 
drop  of  watery  fluid,  which  the  ant  snatches.  This  fluid,  con- 
trary to  prevalent  accounts,  is  not  furnished  by  the  so-called 
honey-tubes  of  the  aphid,  but  comes  from  the  alimentary  canal ; 
the  "  honey-tubes  "  are  glandular  indeed,  but  are  probably 
repellent  in  function.  In  some  instances  ants  give  much  care 
to  their  aphids,  for  example  covering  them  with  sheds  of  mud, 
which  are  reached  through  covered  passagew^ays.  More  than 
this,  however,  some  ants  actually  collect  aphid  eggs  and  pre- 
serve them  over  winter  as  carefully  as  they  do  their  own  eggs. 
In  one  such  instance,  Lubbock  found  that  the  aphids  upon 
hatching,  after  six  months,  were  brought  out  by  the  ants  and 
placed  upon  young  shoots  of  the  English  daisy,  their  proper 
food  plant.  In  our  own  country,  as  Forbes  has  discovered, 
the  eggs  of  the  corn  root  louse  (Aphis  maid irad ids)  are  col- 
lected in  autumn  by  ants  (especially  of  the  genus  Lasiiis)  and 
stored  in  the  underground  nests.  In  winter,  the  eggs  are  taken 
to  the  deepest  parts  of  the  nest,  and  on  bright  spring  days  they 
are  brought  up  and  even  scattered  about  temporarily  in  the 
sunshine;  while  if  a  nest  is  opened,  the  ants  carry  off  the  aphid 
eggs  as  they  would  their  own.  In  spring,  the  ants  tunnel  to 
the  roots  of  pigeon  grass  and  smartweed,  seize  the  aphids  and 
carry  them  to  these  roots,  and  later  to  the  roots  of  Indian 
corn.  Throughout  the  year  the  ants  exercise  supervision  over 
these  aphids ;   occasionally,   as   Forbes   says,   an   ant   seizes   a 


342  ENTOMOLOGY 

winged  louse  in  the  field  and  carries  it  down  out  of  sight,  and 
in  one  such  instance  it  appeared  that  the  wings  had  been 
gnawed  away  near  the  body,  as  if  to  prevent  the  escape  of 
the  louse.  Similar  relations  exist  also  between  ants  and  some 
species  of  scale  insects. 

Guests. — Though  Aphides  and  CoccidcT  are  able  almost 
always  to  live  without  the  help  of  ants,  there  are  some  insects 
which  have  never  been  found  outside  the  nests  of  ants.  Most 
of  these  insect  guests  are  beetles,  notably  Staphylinidae  and 
Pselaphidae.  The  rove-beetles  make  themselves  useful  by 
devouring  refuse  organic  matter,  and  these  scavengers  are  un- 
molested by  the  ants  with  which  they  live.     A  few  myrme- 

FlG.  286. 


Lomcchusa  stniinosa  being  freed  of  mites  by  Dinarda  dentata. — After   Wasmann. 

cophilous  beetles  furnish  their  hosts  with  a  much-coveted  secre- 
tion and  receive  every  attention  from  the  ants,  which  clean 
these  valuable  beetles  and  even  feed  them  mouth  to  mouth,  as 
the  ants  feed  one  another.  Lomechusa  (Fig.  286)  is  one  of 
these  favored  guests,  as  it  has  abdominal  tufts  of  hairs  from 
which  the  ants  secure  a  secreted  fluid.  Atcniclcs  (Fig.  287) 
is  another ;  it  solicits  and  obtains  food  from  the  mouth  of  a 
foraging  ant  as  if  it  were  an  ant  itself.      In  the  Alleghanies, 


INTERRELATIONS    OF    INSECTS 


343 


Afciiirli's  cdT'd  occurs  in  the  nests  of  Fonuica  nifa,  and  is  much 
])rize(l  l)y  this  ant  on  account  of  tlie  lluid  wliicli  the  1)eetlc 
secretes  from  g'lanchilar  hairs  on  the  sides  of  tlie  alxlomen. 
The  beetle  Clavii^cr  has  at  the  base  of  each  elytron  a  tuft 
of  hairs,  which  the  ants  lick  persistently.      This  ])eetle  is  Ijlind 

Fig.  287. 


Atemclcs  emarginatiis  being  fed  by  an  ant,  lilynnica  scahrinodis. — After  Wasmann. 

and  appears  to  be  incapable  of  feeding  itself;  for  when  de- 
l)rived  of  ant-assistance  it  dies,  even  though  surrounded  by 
food.  These  cases  of  symbiosis,  or  mutual  benefit,  are  well 
authenticated. 

Visitors. — Many  myrmecophilous  insects  are  not  restricted 
to  ants'  nests,  but  are  free  to  enter  or  to  leave.  This  is  true  of 
such  Staphylinidse  as  visit  formicaries  simply  for  shelter  or  to 
feed  upon  detritus,  and  these  visitors  are  treated  with  indif- 
ference by  the  ants. 

Intruders. — Not  so.  however,  with  species  that  are  inimical 
to  the  interests  of  the  ants,  such  as  many  species  of  Staphy- 
linidfe  and  Histerid?e,  which  steal  food  from  the  ants,  kill 
them  or  devour  their  larvje  or  pupse  at  every  opportunity. 
The  ants  are  hostile  to  these  marauders,  though  the  latter  often 
escape  through  their  agility  or  else  rely  upon  their  armor  for 
protection.  Oiicdius  brcz'is  and  Myniicdoiiia,  as  Schwarz 
observes,  are  soft-bodied  forms  which  remain  beside  the  walls 
of  the  galleries  or  near  the  entrance  of  a  nest  and  attack  soli- 
tary ants;  while  Hctccriiis,  which  mixes  with  the  ants,  is  pro- 


344 


ENTOMOLOGY 


tected  by  its  hard  and  smooth  covering,  under  which  the  legs 
and  antennae  can  be  withdrawn.  Such  an  enemy  is  an  un- 
avoidable evil  from  the  standpoint  of  an  ant. 

Janet  has  described  the  amusing  way  in  which  an  audacious 
species  of  Lcpismina  steals  food  from  the  very  mouths  of  ants. 
As  is  well  known,  ants  are  accustomed  to  feed  one  another 
from  mouth  to  mouth.  When  the  foragers,  filled  with  honey 
or  other  food,  return  to  the  nest,  they  are  solicited  for  food 
by  those  that  have  remained  at  home ;  as  a  forager  and  a  beg- 
gar stand  head  to  head,  the  former  disgorges  small  drops  of 

Fig.  288. 


Lepismina  stealing  food  from  a  pair  of  ants. — After  Janet. 

food,  which  are  seized  by  the  latter.  While  a  pair  of  ants  are 
engaged  in  this  performance  (Fig.  288).  and  a  drop  of  honey 
is  being  passed,  the  Lepismina  rushes  in,  grabs  the  drop  and 
hurries  away.     As  might  be  expected,  these  interlopers  are 


the  nest  to  another. 

Parasites. — Nematode  worms  occupy  the  pharyngeal  glands 
of  ants ;  larvae  of  Sfylops  inhabit  their  bodies ;  more  than  thirty 
kinds  of  mites  attach  themselves  to  the  heads  or  feet  of  ants; 
while  ChalcididcC  and  Proctotrypid?e  parasitize  ants'  eggs. 


CHAPTER    XI 

INSECT    BEHAVIOR 

1lie  subject  of  insect  behavior  will  be  considered  under  three 
heads:  (i)  Tropisms,  (2)  Instinct,  (3)  Intelligence. 

I.  Tropisms 

Environmental  influences,  such  as  light,  temperature  or 
moisture,  may  control  the  direction  of  locomotion  of  an  organ- 
ism by  determining  the  orientation  of  its  l)ody.  The  reaction 
of  the  organism  under  these  circumstances  is  known  as  a 
tropic,  or  tactic,  reaction.  A  moth,  for  example,  flies  tow^ard 
a  flame — is  positively  pJiototropic ;  a  cockroach,  on  the  con- 
trary, avoids  the  light — is  negatively  pJiototropic.  A  plant 
turns  toward  the  sun — in  other  words,  is  positively  lielio- 
tropic. 

An  insect  flies  toward  the  light  as  inevitably  and  as  mechan- 
ically as  a  i)lant  turns  toward  the  sun ;  indeed,  the  tw^o  phenom- 
ena are  fundamentally  the  same.  Some  students,  however, 
prefer  to  use  the  term  taxis  for  bodily  movements  of  motile 
organisms,  and  the  term  tropisin  for  turning-  movements  of 
fixed  organisms. 

The  study  of  tropic  reactions,  though  comparatively  new, 
has  already  illuminated  the  whole  subject  of  the  behavior  of 
organisms  and  placed  it  on  a  rational  basis.  The  complex 
tropisms  of  insects  offer  a  fresh  and  large  field  to  the  investi- 
gator, comparatively  little  having  as  yet  been  published  upon 
the  subject. 

Chemotropism. — Positive  and  negative  cheiiiotropisiii,  as 
Wheeler  observes,  "  are  among  the  most  potent  factors  in  the 
lives  of  insects."  Insects  are  affected  positively  or  negatively 
by  such  substances  as  can  affect  their  end-organs  of  smell  or 
taste.      Positive   chemotropism   enables   many   insects   to   find 

345 


346  ENTOMOLOGY 

their  food  or  their  mates ;  and  negative  chemotropism  enables 
them  to  avoid  injurious  substances.  This  negative  reaction 
on  the  part  of  other  organisms  is  made  use  of  also  by  such 
insects  as  emit  repellent  odors. 

A  maggot  orients  its  body  with  reference  to  a  source  of 
food  and  then  moves  toward  the  food  just  as  mechanically  as 
a  moth  flies  to  a  flame.  The  maggot,  as  Loeb  maintains,  is 
influenced  chemically  by  the  radiating  diffusion  from  a  piece 
of  meat,  and  follows  a  line  of  diffusion  to  the  center  of  diffu- 
sion in  much  the  same  way  that  a  moth  follows  a  ray  of  light 
to  its  source.  In  both  cases  a  stimulus  affects  muscular  tissue ; 
the  animal  orients  its  body  until  the  muscular  tension  is  sym- 
metrically distributed,  and  then  locomotion  brings  the  animal 
to  the  source  of  the  stimulus,  whether  it  be  food  or  light  or 
something  else. 

The  remarkable  "  instinctive  "  action  of  the  fly  in  laying 
her  eggs  on  meat  is  due,  according  to  Loeb,  simply  to  the  fact 
that  both  the  fly  and  the  maggot  have  the  same  kind  of  posi- 
tive chemotropism.  Similarly  also  in  the  case  of  such  butter- 
flies or  other  insects  as  lay  their  eggs  on  a  special  kind  of  plant. 
It  is  certain  that  "  neither  experience  nor  volition  plays  any 
part  in  these  processes." 

Hydrotropism. — Wheeler  observed  that  beetles  of  the  gen- 
era Haliplits  and  Hydropunis  were  positively  Jiydrotropic ;  that 
when  released  on  the  shore  from  a  bunch  of  water  plants,  they 
scrambled  toward  the  lake,  twenty  feet  away.  Collectors  take 
advantage  of  the  negative  hydrotropism  of  Bcinhidiuui, 
Elaphrus,  OmopJwon  and  other  shore-dwelling  beetles  by 
splashing  the  water  upon  the  dry  bank,  when  the  beetles  leave 
their  places  of  concealment  and  are  easily  caught. 

It  is  well  known  that  after  a  rain  ants  carry  their  young  out 
into  the  sunshine,  though  when  the  upper  parts  of  the  nest 
become  too  dry,  the  ants  transfer  their  eggs,  larv?e  and  pupae 
to  lower  and  moister  galleries.  In  these  instances,  however, 
we  have  to  deal  with  thcnnotropism  as  well  as  hydrotropism. 

Thigmotropism. — Negative  thigiiwfropisiii,  as  displayed  in 


INSECT    BEHAVIOR  34/ 

the  withdrawal  from  contact,  is  a  common  iiliencimenon  amon«- 
animals,  from  T'rotozoa  to  X'ertcbrata.  and  is  often  conducive 
to  the  safety  of  an  organism ;  though  the  negative  response 
occurs  none  the  less,  whether  it  is  to  prove  useful  or  not.  and 
occurs  as  automatically  as  the  collapse  of  a  sensitive  plant  at 
a  touch.  • 

Positive  thig-motropism  is  less  common,  though  nevertheless 
widespread  among  animals.  Protozoa  and  Infusoria  cling  to 
solid  bodies  and  become  aggregated  about  them.  Cockroaches 
squeeze  themselves  into  crevices  until  their  bodies  come  into 
close  contact  with  surrounding  surfaces.  A  moth,  Pyrophila 
{Ainphipyra)  pyrainidoidcs,  is  accustomed  to  squeeze  into 
crevices  under  loose  bark  or  elsewhere,  though  this  habit, 
though  doubtless  protective,  is  not  performed  for  the  purpose 
of  self-concealment.  That  this  is  not  a  case  of  negative  photo- 
tropism.  it  was  proved  by  Loeb,  who  wrote :  "  I  placed  some 
of  these  animals  in  a  box,  one-half  of  which  was  covered  with 
a  non-transparent  body,  the  other  half  with  glass.  I  covered 
the  bottom  of  the  box  with  small  glass  plates  which  rested  on 
small  blocks,  and  were  raised  just  enough  from  the  bottom  to 
allow  an  Ainphipyra  to  get  under  them.  Then  the  Ainphipyra 
collected  under  the  little  glass  plates,  where  their  bodies  w-ere 
in  contact  with  solid  bodies  on  every  side,  not  in  the  dark  cor- 
ner wdiere  they  would  have  been  concealed  from  their  enemies. 
They  even  did  this  when  in  so  doing  they  were  exposed  to 
direct  sunlight.  This  reaction  also  occurred  when  the  whole 
box  was  dark.  It  was  then  impossible  for  anything  but  the 
stereotropic   [thigmotropic]   stimuli  to  produce  the  reaction." 

Rheotropism.  —  Fishes  swimming  or  heading  directly 
against  a  current  of  water  illustrate  positive  rheotropism. 
When  facing  the  current,  the  resistance  of  the  water  is  sym- 
metrically distributed  on  the  body  of  the  animal  and  is  met 
by  symmetrical  muscular  action,  in  the  most  economical  man- 
ner. Many  aquatic  insects  offer  such  examples  of  rheotropism, 
either  positive  or  negative. 

Anemotropism. — Various  flies  orient  the  body  with  refer- 


34c>  ENTOMOLOGY 

ence  to  the  direction  of  the  wind.  AMieeler  observed  swarms 
of  the  male  of  Bibio  alhipennis  poising  in  the  air,  with  all  the 
flies  headed  directly  toward  the  gentle  wind  that  was  blowing. 
If  the  wind  shifted,  the  insects  at  once  changed  their  position 
so  as  again  to  face  to  windward ;  a  strong  wind,  however,  blew 
them  to  the  grcTund.  The  males  of  an  anthomyiid  (Ophyra 
Iciicostoiiia) .  accdrding  to  the  same  naturalist,  hover  in  swarms 
in  the  shade  for  liours  at  a  time;  if  the  breeze  subsides  they 
lose  their  definite  orientation,  but  if  it  is  renewed  they  face 
the  wind  with  military  precision.  In  Syrphidse,  he  finds,  either 
males  or  females  are  positively  ancinotropic.  The  midges  of 
the  genus  Chirojioiinis,  which  on  summer  days  dance  in  swarms 
for  hours  over  the  same  spot,  orient  themselves  to  every  pass- 
ing breeze.  So  also  in  the  case  of  Empididne.  which  Wheeler 
has  observed  swarming  in  one  spot  every  day  for  no  less  than 
two  weeks,  possibly  on  account  of  "  some  odor  emanating  from 
the  soil  and  attracting  and  arresting  the  flies  as  they  emerged 
from  their  pup?e." 

The  Rocky  Mountain  locusts  "  move  with  the  wind  and 
when  the  air-current  is  feeble  are  headed  away  from  its 
source";  when  the  wind  is  strong,  however,  they  turn  their 
heads  toward  it. 

Anemotropism  and  rheotropism  are  closely  allied  phenom- 
ena. As  A\'heeler  says.  "  The  poising  fly  orients  itself  to  the 
wind  in  the  same  way  as  the  swimming  fish  heads  upstream." 
adjusting  itself  to  a  gaseous  instead  of  a  liquid  current.  "  In 
both  cases  the  organism  naturally  assumes  the  position  in 
which  the  pressure  exerted  on  its  surface  is  symmetrically  dis- 
tributed and  can  be  overcome  by  a  perfectly  symmetrical  action 
of  the  musculature  of  the  right  and  left  halves  of  the  body." 

Geotropism, — Gravity  frequently  determines  the  orienta- 
tion and  direction  of  locomotion  of  an  animal.  A  freshly 
emerged  moth  hangs  with  the  abdomen  downward  and  re- 
mains in  this  position  until  the  wings  have  expanded.  Certain 
dolichopodid  flies  found  on  the  bark  of  trees  "  rest  or  walk 
with  the  long  axis  of  the  body  perpendicular  to  the  earth  and 


INSECT    BEHAVIOR 


349 


parallel  with  the  lonq-  axis  of  the  trunk  of  the  tree  and  the 
head  pointing-  upwards.  When  disturbed  they  tly  off,  but 
very  soon  alis^iit  nearer  the  earth  and  ag'ain  walk  upward." 
(Wheeler.)  Coccinelli(l;e  and  cockroaehes  are  also  neg'atively 
gcotropic.  ddie  latter  insects,  as  Loeb  has  obser\ed,  tend  to 
leave  a  horizontal  surface  but  come  to  rest  on  a  surface  that 
is  vertical  or  as  nearly  so  as  i)ossible. 

Wheeler  says,  "  Geotropic  as  well  as  anemotro]:)ic  orienta- 
tion is  not  altered  for  the  sake  of  response  to  lig^ht.  Even  if 
the  insect  be  strongly  heliotropic,  as  is  the  case  in  most  Dip- 
tera,  it  orients  itself  to  the  wind  or  to  gravity  no  matter 
whence  the  light  may  fall." 

Phototropism. — It  is  a  matter  of  common  observation  that 
house  flies,  butterflies,  bees  and  many  other  diurnal  insects  fly 
toward  the  light ;  and  that  cockroaches  and  bedbugs  avoid  the 
light.  These  are  familiar  examples  of  pJiotofropism,  or  the 
"  control  of  the  direction  of  locomotion  by  light."     The  pho- 


A,  tracks  made  on  paper  by  a  larva  of  Liicilia  cccsar  moving  out  of  a  spot  of  ink 
under  the  influence  of  light;  A  and  B  show  respectively  the  first  and  second 
directions  of  the  light.     B,  tracks  made  in  the   dark. — After  Pouchet. 


350  ENTOMOLOGY 

totropic  response  is  either  positive  or  negative  according  as 
the  organism  moves,  respectively,  toward  or  away  from  the 
source  of  Hght.  Maggots  of  Lucilia  cccsar  and  of  many  other 
fiies  are  negatively  phototropic  as  a  rule  (Fig.  289,  A),  but  in 
the  absence  of  light  (other  directive  stimuli  being  excluded,  of 
course)  wander  about  indifferently  (Fig.  289.  B) . 

Do  the  different  rays  of  the  spectrum  differ  in  phototropic 
power?  This  question  has  occurred  to  many  investigators, 
who  have  found  that,  in  general,  the  rays  of  shorter  wave 
length,  as  violet  or  blue,  are  more  effective  than  those  of  longer 
wave  length,  as  yellow  or  red;  the  latter  in  fact  acting  like 
darkness.  Ants  avoid  violet  rays  as  they  would  avoid  direct 
sunlight,  but  carry  on  their  operations  under  yellowish  red  light 
as  they  would  in  darkness.  Miss  Fielde  has  made  use  of  this 
fact  in  studying  the  habits  of  ants,  by  using  as  a  cover  for  her 
artificial  formicaries  an  orange-red  sheet  of  glass  such  as  the 
photographer  uses  for  his  dark  room.  Though  ants  avoid 
violet  rays,  they  prefer  them  to  ultra-violet  rays,  as  Lubbock 
found ;  though  the  latter  rays  produce  no  sensible  effect  on  the 
human  organism. 

These  responses  to  light  are  inevitable  on  the  part  of  the 
organism,  whether  they  are  beneficial  or  harmful,  and  it  is  now 
becoming  recognized  that  the  reactions  of  both  plants  and  ani- 
mals to  light  are  fundamentally  the  same. 

Phototaxis  and  Photopathy. — A  phototropic  organism,  if 
bilaterally  symmetrical,  orients  itself  with  the  head  directly 
toward  or  else  directly  away  from  the  source  of  light  and 
moves  toward  or  away  from  the  light,  as  the  case  may  be.  In 
either  event  the  long  axis  of  the  organism  becomes  parallel 
with  the  rays  of  light.  Now  a  ray  of  light  is  ever  diminishing 
in  intensity  from  its  source,  and  it  would  seem  that  differences 
of  intensity  along  the  paths  of  light  rays  determine  the  orien- 
tation and  consequent  direction  of  locomotion  of  the  organism. 
Some  investigators,  however,  distinguish  between  the  effects 
of  intensify  of  light  and  those  of  its  direction.  Thus  by  in- 
geniously contrived  experiments,  it  has  been  found,  apparently, 


INSECT    BEHAVIOR  351 

that  Protista  (Stvashuvger)  .Dal^Juiia  (Davenport  and  Cannon) 
and  the  caterpillars  of  Povtlicsia  (  Loeb)  move  toward  a  source 
of  lig'ht  even  while,  in  so  doin^-,  thev  are  passing-  into  reg"ions 
of  /(\s\s-  intensity  of  illumination,  l^'or  this  migration  as  deter- 
mined by  the  direction  of  the  light  rays,  the  term  pliototaxis 
is  by  some  authors  (as  Davenport)  reserved.  Usually,  how- 
ever, the  direction  of  locomotion  docs  depend  on  differences 
of  intensity,  without  regard  to  the  direction  whence  the  light 
comes.  This  "  migration  towards  a  region  of  greater  or  less 
intensity  of  light  "  has  been  termed  pliotopathy,  and  organisms 
are  said  to  be  photo pliil  or  pliotophob,  according  as  they  move, 
respectively,  toward  or  away  from  a  more  intensely  illumi- 
nated area. 

Verworn  and  others  maintain  that  differences  of  intensity 
are  sufificient  to  account  for  all  phototropic  phenomena. 

Optimum  Intensity. — It  has  been  found  that  there  is  a 
certain  optiuiinn  degree  of  light,  differing  according  to  the 
organism,  toward  which  the  organism  will  move,  from  either 
a  region  of  greater  illumination  or  one  of  less.  The  organism 
appears  to  be  attuned  to  a  "  certain  range  of  intensity."  This 
attunement  is  used  by  Davenport  to  explain  apparent  anoma- 
lies between  the  response  to  light  of  a  butterfly  and  that  of  a 
moth.  Butterflies  are  positively  phototropic  to  sunlight  and 
most  moths  are  negatively  so.  Why,  then,  do  moths  fly 
toward  a  lamp  or  an  electric  light  ?  The  answer  is  given  that 
the  moth  is  positively  phototropic  up  to  a  certain  intensity  of 
light,  at  which  it  becomes  negatively  phototropic.  "  Butter- 
flies are  attuned  to  a  high  intensity  of  light,  moths  to  a  low 
intensity ;  so  that  bright  sunlight,  which  calls  forth  the  one, 
causes  the  other  to  retreat.  On  the  other  hand,  a  light  like 
that  of  a  candle,  so  weak  as  not  to  stimulate  a  butterfly,  pro- 
duces a  marked  response  in  the  moth."      (Davenport.) 

The  circling  of  moths  and  other  insects  about  a  light  is  a 
matter  of  common  observation,  an  explanation  for  which  has 
been  given  by  Loeb.  Loeb  says,  "  If  a  moth  be  struck  by  the 
Hght  on  one  side,  those  muscles  which  turn  the  head  toward 


352  ENTOMOLOGY 

the  light  become  more  active  than  those  of  the  opposite  side, 
and  correspondingly  the  head  of  the  animal  is  turned  toward 
the  source  of  light.  As  soon  as  the  head  of  the  animal  has 
this  orientation  and  the  median-plane  (or  plane  of  symmetry) 
comes  into  the  direction  of  the  rays  of  light,  the  symmetrical 
points  of  the  surface  of  the  body  are  struck  by  the  rays  of  light 
at  the  same  angle.  The  intensity  of  light  is  the  same  on  both 
sides,  and  there  is  no  reason  why  the  animal  should  turn  to 
the  right  or  left,  away  from  the  direction  of  the  rays  of  light. 
Thus  it  is  led  to  the  source  of  the  light.  Animals  that  move 
rapidly  (like  the  moth)  get  into  the  flame  before  the  heat  of 
the  flame  has  time  to  check  them  in  their  flight.  Animals  that 
move  slowly  are  afTected  by  the  increasing  heat  as  they  ap- 
proach the  flame ;  the  high  temperature  checks  their  progres- 
sive movement  and  they  walk  or  fly  slowly  about  the  flame." 
As  Loeb  insists,  the  moth  "  does  not  fly  into  the  flame  out  of 
'  curiosity,'  neither  is  it  '  attracted  '  by  the  light ;  it  is  only 
oriented  by  it  and  in  such  a  manner  that  its  median-plane  is 
brought  into  the  direction  of  the  rays  and  its  head  directed 
toward  the  source  of  light.  In  consequence  of  this  orienta- 
tion its  progressive  movements  must  lead  it  to  the  source  of 
light." 

Factors  Infiuencing  Phototropism. — The  response  of  an 
organism  to  light  is  influenced  by  previous  exposure  to  light, 
by  temperature,  moisture,  nutrition  and  other  factors,  all  of 
which  have  to  be  taken  into  account  in  experiments  on  photo- 
tropism. 

Loeb  found  that  larvcX  of  the  moth  Euproctis  elirysorrlicva, 
driven  by  the  warm  sunshine  out  of  the  nest  in  which  they 
have  hibernated,  crawl  upward  to  the  tips  of  branches  and  feed 
upon  the  buds  and  new  leaves.  This  self-preservative  "  in- 
stinct "  is  purely  a  response  to  light.  The  caterpillars  are 
positively  phototropic,  and  as  the  horizontal  components  of  the 
surrounding  light  neutralize  each  other,  only  the  light  from 
above  is  effective  as  a  stimulus  to  orientation.  After  feeding, 
however,  the  larvK  are  no  longer  positively  phototropic  and 


INSECT    BEHAVIOR  353 

crawl  downward ;  in  otlier  words,  they  are  positively  photo- 
tropic  only  so  loiii^-  as  tliey  are  nnfed.  Here  the  kind  of  pho- 
totropism  is  dependent  upon  nutrition. 

Phototropism  may  be  overruled  by  chemotropisni  and  influ- 
enced by  conditions  of  metabolism,  as  Parker  found  for  the 
buttertly  J'aiicssa  autiopa.  In  his  words:  J'aiicssa  oiitioj^a,  in 
brio-ht  sunligiit,  comes  to  rest  widi  the  head  away  from  the 
source  of  light,  that  is,  it  is  neg-atively  phototropic,  when  the 
surface  on  wdiich  it  settles  is  not  perpendicular  or  very  nearly 
perpendicular  to  the  direction  of  the  sun's  rays.  When,  how- 
ever, this  surface  is  perpendicular  to  the  sun's  rays  the  insect 
settles  without  reference  to  the  direction  of  the  rays.  When 
feeding-  or  near  food  [such  as  running-  sap]  the  butterflies  do 
not  respond  phototropically. 

This  negative  phototropism  is  seen  only  in  intense  sunlight 
and  after  the  butterfly  has  been  on  the  wing,  i.  e.,  after  a  cer- 
tain state  of  metabolism  has  been  established. 

V.  antiopa  creeps  and  flies  toward  a  source  of  light,  that  is, 
it  is  positively  phototropic  in  its  locomotor  responses.  Posi- 
tive phototropism  also  occurs  in  intense  sunlight,  and  is  not 
dependent  upon  any  particular  phase  of  metabolism. 

Both  negative  and  positive  phototropism  in  this  species  are 
independent  of  the  "  heat  rays  "  of  sunlight. 

The  position  assumed  in  negative  phototropism  exposes  the 
color  patterns  of  the  wings  to  fullest  illumination,  and  prob- 
ably has  to  do  with  bringing  the  sexes  together  during  the 
breeding  season. 

To  these  may  be  added  other  important  conclusions  of 
Parker's : 

No  light  reactions  are  obtained  from  the  butterfly  when 
shadows  are  thrown  upon  any  part  of  the  body  except  the 
head.  \\'hen  one  eye  is  painted  black  the  butterfly  creeps  or 
flies  in  circles  with  the  unaffected  eye  always  toward  the  cen- 
ter. When  both  eyes  are  painted  black  all  phototropic  re- 
sponses cease  and  the  insect  flies  upward.  Butterflies  with 
normal  eyes  liberated  in  a  perfectly  dark  room  come  to  rest 
24 


354  ENTOMOLOGY 

near  the  ceiling.  This  upward  flight  in  both  cases  is  due  to 
negative  geotropism,  not  to  phototropic  activity. 

['.  antiopa  does  not  discriminate  between  lights  of  greater 
or  less  intensity  provided  they  are  all  of  at  least  moderate 
intensity  and  of  approximately  equal  size.  ]\  antiopa  does 
discriminate  between  light  derived  from  a  large  luminous  area 
and  that  from  a  small  one,  e\'en  when  the  light  from  these  two 
sources  is  of  equal  intensity  as  it  falls  on  the  animal.  These 
butterflies  usually  fly  toward  the  larger  areas  of  light.  This 
species  remains  in  flight  near  the  ground  because  it  reacts  posi- 
tively to  large  patches  of  bright  sunlight  rather  than  to  small 
ones,  even  though  the  latter,  as  in  the  case  of  the  sun,  may  be 
much  more  intense. 

V.  antiopa  retreats  at  night  and  emerg'es  in  the  morning,  not 
so  much  because  of  light  differences,  as  because  of  temperature 
changes.  On  warm  days  it  will,  however,  become  quiet  or 
active,  without  retreating,  depending  upon  a  sudden  decrease 
or  increase  of  light. 

The  maggots  of  the  muscid  Plwnnia  rcgina  are,  as  the 
author  has  observed,  negatively  phototropic  until  full  grown, 
when  they  become  positively  phototropic  for  an  hour  or  less, 
leave  the  decaying  matter  in  which  they  have  developed  and 
wriggle  along  the  ground  toward  the  sun;  or  if  the  sunlight 
is  diffused  by  clouds,  wander  about  aimlessly,  but  at  length 
bury  themselves  in  the  ground  to  pupate.  Here  the  positive 
phototropism  just  before  pupation  is  adaptive,  as  it  is  in  the 
case  of  sexually  mature  ants,  which  make  a  nuptial  flight  into 
the  sunlight  when  they  have  acquired  wings.  The  swarming 
of  the  honey  bee  is  likewise  a  case  of  periodic  positive  photo- 
tropism, as  Kellogg  has  observed. 

Though  adaptive  in  their  results,  these  phototropic  reac- 
tions can  scarcely  be  said  to  be  performed  on  account  of 
their  usefulness.  They  are  performed  anyway,  and  may  re- 
sult harmfully,  as  when  they  lead  a  moth  into  a  flame  or,  to 
take  a  more  natural  example,  when  they  expose  an  insect  to 
its  enemies. 


INSECT    BEHAVIOR  355 

Phototropism  and  thermotropism,  cither  too-cthcr  or  singly, 
as  Wheeler  suggests,  may  explain  the  np  and  d(^wn  migration 
of  insects  in  vegetation.  "  On  cold,  cloudy  days  few  insects 
are  taken  hecause  they  lurk  quietly  near  the  surface  of  the  soil 
and  about  the  roots  of  tlie  vegetation,  l)ut  with  an  increase  in 
warmth  and  light  they  move  upwards  along'  the  stems  and 
leaves  of  the  plants,  and,  if  the  day  be  warm  and  sunny,  escape 
into  the  air." 

Thermotropism. — Ants  are  strongly  thennotropic;  they 
carry  their  eggs,  larvse  and  pupae  from  a  cooler  to  a  warmer 
place  or  vice  versa,  and  thus  secure  optimum  conditions  of 
temperature.  Caterpillars  and  cockroaches  migrate  to  regions 
of  optimum  temperature. 

In  thermotropism  it  appears  that  the  direction  of  heat  rays 
has  little  or  no  effect  as  compared  with  differences  of  intensity. 

Tropisms  in  General. — Other  kinds  of  tropisms  are  known, 
for  example,  tonotropism,  or  the  control  of  the  direction  of 
locomotion  by  density,  and  electrotropism ;  not  to  mention  any 
more. 

All  these  phenomena  are  responses  of  protoplasm  to  definite 
stimuli  and  are  almost  as  inevitable  as  the  response  of  a  needle 
to  a  magnet. 

The  tropisms  of  the  lower  organisms  have  been  experi- 
mented upon  by  many  skilled  investigators,  whose  results  fur- 
nish a  broad  basis  for  the  study  of  the  subject  in  the  higher 
animals — a  study  which  has  scarcely  begun.  Even  in  the 
simplest  organisms,  behavior  is  the  resultant  etTect  of  several 
or  many  stimuli  acting  at  once,  and  the  precise  effect  of  each 
stimulus  can  be  ascertained  only  by  the  most  guarded  kind  of 
experimentation ;  while  in  the  higher  animals,  with  their  com- 
plex organization,  including  specialized  sense  organs,  the  study 
of  behavior  becomes  intricate  and  cannot  be  carried  on  intelli- 
gently without  an  extensive  knowledge  of  the  l^ehavior  of 
unicellular  organisms.  The  properties  of  protoplasm  are  the 
key  to  the  behavior  of  organisms,  though  comparatively  little 
is  known  as  yet  in  regard  to  these  properties.     Furthermore, 


356  ENTOMOLOGY 

the  study  of  tropic  reactions  is  complicated  by  the  fact  that 
they  are  due  not  only  to  external  stimuli,  but  also  to  little- 
understood  internal  stimuli,  arising  from  unknown  conditions 
of  the  alimentary  canal,  reproductive  organs,  etc. 

A  newly  recognized  property  of  protoplasm  is  that  of  adap- 
tation, as  manifested  in  the  acclimatization  of  protoplasm  to 
untoward  conditions  of  temperature,  light,  contact  and  other 
stimuli ;  and  this  adaptation  to  unusual  conditions  may  take 
place  without  the  aid  of  natural  selection. 

A  tropic  reaction  occurs,  whether  it  is  to  prove  useful  to  the 
organism  or  not.  Thus  a  lady-bird  beetle  walks  upward,  on 
a  branch,  on  a  fence,  on  one's  finger.  It  walks  upward  as  far 
as  possible  and  then  flies  into  the  air.  If  it  happens  to  reach 
the  tip  of  a  twig  and  finds  aphids  there,  the  beetle  stops  and 
feeds  upon  them.  This  adaptive  result  is  in  a  sense  incidental 
Yet,  upon  the  whole,  tropic  reactions  are  wonderfully  adaptive 
in  their  results.  Here  natural  selection  is  of  special  value  as 
affording  an  explanation  of  the  phenomena. 

As  Loeb  and  Davenport  have  insisted,  the  mechanical  reac- 
tions to  gravity,  light,  heat  and  other  influences  determine  the 
behavior  of  the  organism. 

2.  Instinct 

Insects  are  eminently  instinctive ;  though  their  automatic 
behavior  is  often  so  remarkably  successful  as  to  appear  ra- 
tional, instead  of  purely  instinctive. 

Instinct,  as  distinguished  from  reason,  attains  adaptive  ends 
without  prevision  and  without  experience.  For  example,  a 
butterfly  selects  a  particular  species  of  plant  upon  which  to  lay 
her  eggs.  Caterpillars  of  the  same  species  construct  the  same 
kind  of  nest,  though  so  isolated  from  one  another  as  to  exclude 
the  possibility  of  imitation.  Every  caterpillar  that  pupates 
accomplishes  the  intricate  process  after  the  manner  of  its  kind, 
without  the  aid  of  experience. 

Instinctive  actions  belong  to  the  reflex  type — they  consist 
of  co-ordinated  reflex  acts.     A  complex  instinctive  action  is  a 


INSECT    BEHAVIOR  357 

chain,  each  hnk  of  which  is  a  simple  reflex  act.  In  fact,  no 
sliarp  hne  can  be  drawn  between  reflexive  and  instinctive 
actions. 

Basis  of  Instinct. — Reflex  acts,  the  elements  from  which 
instinctive  actions  are  compounded,  are  the  inevitable  responses 
of  particular  organs  to  appropriate  stimuli,  and  involve  no 
volition.  The  i)resence  of  an  organ  normally  implies  the 
ability  to  use  it.  The  newly  born  butterfly  needs  no  practice 
preliminary  to  flight.  The  process  of  stinging  is  entirely 
reflex ;  a  decapitated  wasp  retains  the  power  to  sting,  directing 
its  weapon  toward  any  part  of  the  body  that  is  irritated;  and 
a  freshly  emerged  wasp,  without  any  practice,  performs  the 
stinging  movements  with  greatest  precision. 

As  Whitman  observes,  the  roots  of  instincts  are  to  be  sought 
in  the  constitutional  activities  of  protoplasm. 

Apparent  Rationality. — The  ostensible  rationality  of  be- 
havior among  insects,  as  was  said,  often  leads  one  to  attribute 
intelligence  to  them,  even  when  there  is  no  evidence  of  its 
existence.  As  an  illustration,  many  plant-eating  beetles,  when 
disturbed,  habitually  drop  to  the  ground  and  may  escape  detec- 
tion by  remaining  immovable.  We  cannot,  however,  believe 
that  these  insects  "  feign  death  "  with  any  consciousness  of 
the  benefit  thus  to  be  derived.  This  act,  widespread  among 
animals  in  general,  is  instinctive,  or  reflex,  as  Whitman  main- 
tains, being,  at  the  same  time,  one  of  the  simplest,  most  advan- 
tageous and  deeply  seated  of  all  instinctive  performances. 

Take  the  many  cases  in  which  an  insect  lays  her  eggs  upon 
only  one  species  of  plant.  The  philenor  butterfly  hunts  out 
Aristolochia,  which  she  cannot  taste,  in  order  to  serve  larvae, 
of  whose  existence  she  can  have  no  foreknowledge.  Oviposi- 
tion  is  here  an  instinctive  act,  not  performed  until  it  is  evoked 
by  some  sort  of  stimulus — perhaps  an  olfactory  one — from  a 
particular  kind  of  plant. 

Stimuli. — Some  determinate  sensory  stimulus,  indeed,  is  the 
necessary  incentive  to  any  reflex  act.     The  first  movements  of 


358  ENTOMOLOGY 

probably  one  of  temperature.  Simple  contact  with  the  egg- 
shell is  probably  sufficient  to  stimulate  the  jaws  to  work,  and 
the  caterpillar  eats  its  way  out;  yet  it  cannot  foresee  that  its 
biting  is  to  result  in  its  liberation.  Nor,  later  on,  when  vora- 
ciously devouring  leaves,  can  the  caterpillar  be  supposed  to 
know  that  it  is  storing  up  a  reserve  supply  of  food  for  the  dis- 
tant period  of  pupation  and  the  subsequent  imaginal  stage. 
The  ends  of  these  reflex  actions  are  proximate  and  not  ulti- 
mate, except  from  the  standpoint  of  higher  intelligence. 

Just  as  simple  reflexes  link  together  to  form  an  instinctive 
action,  so  may  instincts  themselves  combine.  The  complex 
behavior  of  a  solitary  wasp  is  a  chain  of  instincts,  as  the  Peck- 
hams  have  shown.  All  the  operations  of  making  the  nest, 
stinging  the  prey,  carrying  it  to  the  nest,  etc.,  are  performed 
as  a  rule  in  a  definite,  predicable  sequence,  and  even  a  slight 
interference  with  the  normal  sequence  disconcerts  the  insect. 
Just  as  the  performance  of  one  reflex  act  may  serve  as  the 
stimulus  for  the  next  reflex  in  order,  so  the  completion  of  one 
instinctive  action  may  be  in  part  the  stimulus  for  the  next  one. 

Modification  of  Instincts. — An  action  can  be  regarded  as 
purely  instinctive  in  its  initial  performance  only,  because  every 
subsequent  performance  may  have  been  modified  by  experi- 
ence ;  in  other  words,  habits  may  have  been  forming  and  fix- 
ing, so  that  the  results  of  instinct  become  blended  with  those 
of  experience.  J"hus  the  first  flight  of  a  dragon  fly  is  instinc- 
tive and  erratic,  but  later  efforts,  aided  by  experience,  are  well 
under  control. 

When  once  shaped  by  experience,  reflex  or  instinctive  ac- 
tions tend  to  become  intense  habits.  Thus,  certain  caterpillars, 
having  eaten  all  the  available  leaves  of  a  special  kind,  will 
almost  invariably  die  rather  than  adopt  a  new  food  plant, 
whereas  larvae  of  the  same  species  will  eat  a  strange  plant  if 
it  is  offered  to  them  at  birth.  An  act  is  strengthened  in  each 
repetition  by  the  influence  of  habit,  to  the  increasing  exclusion 
of  other  possible  modes  of  action.  Many  a  caterpillar,  having 
eaten  its  way  out  of  the  egg-shell,  does  not  stop  eating,  but 


INSECT    BEHAVIOR  359 

consumes  the  remainder  of  the  shell — a  rellex  act,  started  by 
a  stimulus  of  contact  against  the  jaws  and  continued  until  the 
cessation  oi  the  stimulus,  unless  some  stronger  stimulus  should 
intervene.  It  has  been  said  that  the  larva  eats  the  remains  of 
the  shell  because  they  might  betray  its  presence  to  its  enemies. 
\\'hether  this  is  true  or  not,  to  assume  conscious  foresight  of 
such  a  result  on  the  part  of  an  inexperienced  caterpillar  is  worse 
than  unnecessary. 

With  insects,  as  with  other  animals,  many  instincts  are 
transitory;  even  A\hen  partially  fixed  by  habit,  they  are  replace- 
able by  stronger  instincts.  Thus  the  gregarious  habit  of  lar- 
vae is  finally  overpowered  by  a  propensity  to  wander,  which 
does  not  mature,  however,  until  the  approach  of  the  transfor- 
mation period.  The  reproductive  instinct  is  another  of  those 
impulses  that  do  not  ripen  until  a  certain  age  in  the  individual. 

Inflexibility  of  Instincts. — Broadly  speaking,  instinctive 
actions  lack  individuality — are  performed  in  the  same  way  by 
every  individual  of  the  species.  The  solitary  wasps  of  the 
same  species  are  remarkably  consistent  in  architecture,  in  the 
selection  of  a  special  kind  of  prey,  in  the  way  they  sting  it, 
carry  it  to  the  nest  and  dispose  of  it ;  all  these  operations,  more- 
over, are  performed  in  a  sequence  that  is  characteristic  of  the 
species.  Examples  of  this  so-called  inflexibility  of  instinct  are 
so  omnipresent,  indeed,  that  insect  behavior  as  a  whole  is 
admitted  to  be  instinctive,  or  automatic.  Insects  are  capable 
of  an  immense  number  of  reflex  impulses,  ready  to  act  singly 
or  in  intricate  correlation,  upon  the  recjuisite  stimuli  from  the 
environment. 

To  normal  conditions  of  the  environment,  the  behavior  of 
an  insect  is  accurately  adjusted ;  in  the  face  of  abnormal  cir- 
cumstances, however,  demanding  the  exercise  of  judgment, 
most  insects  are  helpless.  The  specialization  to  one  kind  of 
food,  though  usually  advantageous,  is  fatal  if  the  supply  be- 
comes insufficient  and  the  larva  is  unable  to  adopt  another 
food.  A  species  of  Sphc.v  habitually  drags  its  grasshopper 
victim  by  one  antenna.     Fabre  cut  of¥  both  antennae  and  then 


36o 


ENTOMOLOGY 


found  that  the  Sphcx,  after  vain  efforts  to  secure  its  customary 
hold,  abandoned  the  prey.  Under  such  unaccustomed  condi- 
tions, insects  often  show  a  surprising-  stupidity,  capable  as  thev 
are  amid  ordinary  circumstances. 

Flexibility  of  Instincts. — Notwithstanding  such  examples, 
the  common  assertion  that  instincts  are  absolutely  "  blind,"  or 
inflexible,  is  incorrect.  Instinctive  acts  are  not  mechanically 
invariable,  though  their  variations  are  so  inconspicuous  as 
frequently  to  escape  casual  observation.  A  precise  observer 
can  detect  individual  variations  in  the  performance  of  any 
instinctive  act — variations  analogous  to  those  of  structure. 

Fig.  290. 


Ammophila   urnaria   using   a   stone   to   pound    down   the    earth    over    her    nest.     Greatly 
enlarged. — After  Peckham,   from   Bull.   Wisconsin  Geol.   and  Nat.   Hist.   .Survej-. 


To  take  extreme  examples,  the  Peckhams  found  that  an 
occasional  queen  of  Polistes  fiisca  would  occupy  a  comb  of  the 
previous  year,  instead  of  building  a  new  one ;  and  that  an  indi- 
vidual of  Pompilus  marginatiis,  instead  of  hiding  her  captured 
spider  in  a  hole  or  imder  a  lump  of  earth  as  usual,  hung  it  up 
in  the  fork  of  a  purslane  plant.  They  observed  also  that  one 
AiiimopJiila,  in  order  to  pound  down  the  earth  over  her  nest, 
actually  used  a  stone,  held  between  the  mandibles  (Fig.  290). 

While  most  of  the  variations  that  one  encounters  are  small 


INSECT    BEHAVIOR  3^1 

and,  in  a  sense,  accidental,  or  purposeless,  such  novel  depart- 
ures as  those  of  the  Polisfrs  or  the  Amuiol^Jiihi  would  seem  to 
denote  adaptability. 

Even  the  despotic  power  of  habit  may  be  ovcrl)orne  Ijy  indi- 
vidual adaptability.  Among  caterpillars  that  have  exhausted 
their  customary  food,  there  are  often  a  few  that  will  adopt  a 
new  food  plant  and  survive,  leaving'  their  more  conservative 
fellows  to  starve. 

As  Darwin  himself  held,  the  doctrine  of  natural  selection  is 
applicable  to  instincts  as  well  as  structures.  All  reflex  acts  are 
to  some  extent  variable.  Disadvantageous  reflexes  or  combi- 
nations of  reflexes  eliminate  themselves,  wdiile  advantag"eous 
ones  persist  and  accumulate. 

Indeed,  structures  and  instincts  must  frequently  have 
evolved  hand  in  hand.  The  remarkable  protective  resemblance 
of  the  KaUiina  butterfly  would  be  useless,  did  not  the  insect 
instinctively  rest  among  dead  leaves  of  the  appropriate  kind. 

Origin  of  Instinct. — There  are  two  leading  theories  as  to 
the  origin  of  instinct.  Lamarck,  Romanes  and  their  followers 
have  regarded  instinct  as  inherited  habit ;  have  supposed  that 
instincts  have  originated  by  the  relegation  to  the  reflex  type  of 
actions  that  at  first  were  rational,  and  that  instincts  represent 
the  accumulated  results  of  ancestral  experience.  This  habit 
theory,  however,  has  little  to  support  it,  and  assumes  the  in- 
heritance of  accjuired  characters — which  has  not  been  proved. 

The  selection  theory  of  Darwin,  Weismann,  Morgan  and 
others  has  much  in  its  favor.  It  regards  reflex  acts  as  primi- 
tive, as  the  raw  material  from  which  natural  selection,  as  the 
chief  factor,  has  effected  those  combinations  that  are  termed 
instincts. 

Instincts  and  Tropisms. — We  have  already  emphasized 
the  fact  that  an  instinct  is  a  reflex  act  or  a  combination  of 
reflex  acts.  The  same  fact  may  now  be  stated  in  these  words  : 
an  instinct  is  a  tvopism  or  a  combination  of  tropisms.  The 
more  important  of  these  tropisms  have  been  considered. 
Whenever  possible  it  is  better  to  discard  the  ambiguous  term 


3^2  ENTOMOLOGY 

instinct  in  favor  of  such  more  precise  terms  as  phototropism, 
geotropism,  etc. ;  thoug-h  the  term  instinct  remains  useful  as 
appHed  to  an  action  that  is  the  resukant  of  several  tropic 
responses. 

The  modern  student  of  instincts  aims  to  resolve  them  into 
their  component  reflexes  and  to  determine  as  precisely  as  pos- 
sible the  influence  of  each  reflex  component.  Thanks  to  the 
labors  of  a  great  number  of  skilled  investigators,  we  are  no 
longer  satisfied  to  class  an  action  as  "  instinctive  "  and  then 
dismiss  it  from  thought ;  for  now  we  are  in  a  position  to 
analyze  the  action,  and  may  hope  to  explain  it  eventually  in 
terms  of  the  physical  and  chemical  properties  of  protoplasm. 

3.   Intelligence 

Though  manifestly  dominant,  pure  instinct  fails  to  account 
for  all  insect  behavior.  The  ability  of  an  insect  to  profit  by 
experience  indicates  some  degree  of  intelligence. 

Take,  for  example,  the  precision  with  which  bees  or  wasps 
find  their  way  back  to  the  nest.  This  is  no  longer  to  be 
accounted  for  on  the  assumption  of  a  mysterious  "  sense  of 
direction,"  for  there  is  the  best  of  evidence  for  believing  that 
it  depends  upon  the  recognition  of  surrounding  objects. 
When  leaving  the  nest  for  the  first  time,  these  insects  make 
"  locality  studies,"  which  are  often  elaborate.  Referring  to 
Sphex  ichnciiinonca,  the  Peckhams  write:  ''At  last,  the  nest 
dug,  she  was  ready  to  go  out  and  seek  for  her  store  of  pro- 
vision and  now  came  a  most  thorough  and  systematic  study 
of  the  surroundings.  The  nests  that  had  been  made  and  then 
deserted  had  been  left  without  any  circling.  Evidently  she 
was  conscious  of  the  difference  and  meant,  now,  to  take  all 
necessary  precautions  against  losing  her  way.  She  flew  in  and 
out  among  the  plants  first  in  narrow  circles  near  the  surface 
of  the  ground,  and  now  in  wider  and  wider  ones  as  she  rose 
higher  in  the  air,  until  at  last  she  took  a  straight  line  and 
disappeared  in  the  distance.  The  diagram  [Fig.  291,  A] 
gives  a  tracing  of  her  first  study  preparatory  to  departure. 


INSECT    BEHAVIOR 


1>^Z 


\e\'\  often  after  one  thorcmt^'h  study  of  the  topog-raphy  of  her 
liome  has  l)een  made,  a  wasp  goes  away  a  second  time  with 
much  less  circhng  or  with  none  at  all.  The  second  diagram 
[Fig.  291,  5]  gives  a  fair  illustration  of  one  of  these  more 
hasty  departures.  .  .  . 

"  If  the  examination  of  the  objects  about  the  nest  makes  no 
impression  upon  the  wasp,  or  if  it  is  not  remembered,  she  ought 
not  to  be  inconvenienced  nor  thrown  off  her  track  when  weeds 
and  stones  are  removed  and  the  surface  of  the  ground  is 
smoothed  over;  but  this  is  just  what  happens.     Aponis  fasci- 


FiG.  291. 


Locality    studies    made    by    a   wasp,    Sphe.v   iciuieumonea.     A,    a   thorough    study; 
a  hasty  study;   n,  nest.     After   Peckham,    from   Bull.   Wisconsin   Geol.   and   Nat.   Hist. 
Survey. 


atus  entirely  lost  her  way  when  we  broke  off  the  leaf  that 
covered  her  nest,  but  found  it  without  trouble,  when  the  miss- 
ing object  was  replaced.  All  the  species  of  Ccrccvis  were  ex- 
tremely annoyed  if  we  placed  any  new  object  near  their  nest- 
ing-places. Our  Amnio phila  refused  to  make  use  of  her  bur- 
row after  w-e  had  drawn  some  deep  lines  in  the  dust  before  it. 
The  same  annoyance  is  exhibited  when  there  is  any  change 


3^4  ENTOMOLOGY 

made  near  the  spot  upon  which  the  prey  of  the  wasp,  whatever 
it  may  be,  is  deposited  temporarily." 

If  we  take,  as  one  criterion  of  intelHgence.  the  power  to 
choose  between  ahernatives,  then  insects  are  more  intelHgent 
than  is  generally  admitted.  The  control  of  locomotion,  the 
selection  of  prey,  and  the  avoidance  of  enemies,  as  results  of 
experience,  indicate  powers  of  discrimination.  The  power  of 
intercommunication,  conceded  to  exist  among  the  social  Hy- 
menoptera,  implies  some  degree  of  intelligence. 

If  instinct  is  blind,  or  mechanical,  with  no  adjustment  of 
means  to  ends,  then  a  pronounced  individuality  of  action  must 
signify  something  more  than  instinct — as  in  the  case  of  the 
Ammophila.  In  regard  to  a  female  Poinpiliis  scelcstiis,  which 
had  dragged  a  large  spider  nearly  to  her  nest,  the  Peckhams 
observe :  "  Presently  she  went  to  look  at  her  nest  and  seemed 
to  be  struck  with  a  thought  that  had  already  occurred  to  us — 
that  it  was  decidedly  too  small  to  hold  the  spider.  Back  she 
went  for  another  survey  of  her  bulky  victim,  measured  it  with 
her  eye,  without  touching  it,  drew  her  conclusions,  and  at  once 
returned  to  the  nest  and  began  to  make  it  larger.  \\'"e  have 
several  times  seen  wasps  enlarge  their  holes  when  a  trial  had 
demonstrated  that  the  spider  would  not  go  in,  but  this  seemed 
a  remarkably  intelligent  use  of  the  comparative  faculty." 

From  the  standpoint  of  pure  instinct,  indeed,  much  of  the 
behavior  of  the  solitary  wasps  is  inexplicable ;  while  the  actions 
of  the  social  Hymenoptera  ha\"e  led  some  of  the  most  critical 
students  to  ascribe  intelligence  to  these  insects.  The  activities 
of  the  harvesting  ants,  the  military  or  the  slave-holding  species, 
are  of  such  a  nature  that  the  possibility  of  education  by  experi- 
ence and  instruction  is  strong,  to  say  the  least.  In  fact,  Forel 
has  maintained  that  a  young  ant  is  actually  trained  to  its 
domestic  duties  by.  its  older  companions.  Miss  Enteman,  on 
the  contrary,  says :  '*  \\'asps  do  not  imitate  one  another.  In- 
stinct and  individual  experience  account  sufficiently  for  their 
powers,  and  their  apparent  cooperation  is  due  entirely  to  the 
accident  of  their  beinsf  born  in  the  same  nest."     She  finds  that 


INSECT    BEHAVIOR  365. 

the  worker  Polisirs  dcies  n^t  learn  to  feed  the  larv.x  l)y  imi- 
tating the  (|neen. 

It  is  extremely  difficnlt.  however,  if  not  impossible,  to  draw 
the  line  between  instinct  and  intelligence ;  and  in  doubtful  cases 
there  is  a  general  tendency  to  exaggerate  the  importance  of 
intelligence  rather  than  that  of  instinct.  For  example,  the 
well-known  discrimination  on  the  part  of  ants  between  mem- 
bers of  their  own  colony  and  those  of  other  colonies,  even  of 
the  same  species,  would  seem  tn  impl}-  intelligent  rec(^gnition. 
This  recognition,  h(.)wever,  is  due  simply  to  a  characteristic 
odor,  which  is  derived  from  the  mother  of  the  community. 
An  ant  after  being  washed  receives  hostile  treatment  from 
others  of  its  own  colony;  while  an  alien  ant  after  being 
smeared  with  the  juices  of  hostile  ants  is  treated  by  the  latter 
as  a  friend. 

Each  instance  of  apparent  intelligence  must  be  examined 
impartially  on  its  own  merits.  At  present  it  may  be  said  that, 
while  most  of  the  behavior  of  insects  is  purely  instinctive,  there 
is  some  reason  to  believe  that  at  least  gleams  of  intelligence 
appear  in  the  most  specialized  Hymenoptera. 

Lack  of  Rationality. — However  intelligent  the  social  Hy- 
menoptera may  be  in  their  way,  they  show  no  signs  of  the 
power  of  abstract  reasoning.  Even  ants,  according  to  the 
experiments  of  Lubbock,  display  profound  stupidity  in  the 
face  of  novel  emergencies  wdien  they  might  extricate  them- 
selves by  abstract  reasoning  of  the  simplest  kind.  The 
thoughts  of  an  ant  or  bee  seem  to  be  limited  to  simple  associa- 
tions of  concrete  things.  Aliss  Enteman  observed  a  Polistcs 
worker  which  gnawed  a  piece  out  of  the  side  of  a  dead  larva 
of  its  own  kind  and,  turning,  actually  offered  it  as  food  to  the 
mouth  of  the  same  larva.  In  another  instance,  a  larA'a  was 
attacked  and  killed,  and  then  offered  a  piece  of  its  owm  body. 

Such  examples  as  these  emphasize  the  strength  of  the  reflex 
factor  in  the  behavior  of  insects.  Indeed,  the  basis  of  all 
behavior  is  being  sought  in  the  reactions  of  protoplasm  to 
external  stimuli.  Possibly  even  memory,  consciousness  and 
other  attributes  of  intelligence  will  eventually  be  reduced  to 
this  basis,  improbable  as  it  may  now^  seem. 


CHAPTER    XII 

DISTRIBUTION 

I.  Geographical 

Importance  of  Dispersion. — Dispersion  enables  species  to 
mitigate  the  intense  competition  and  the  rigid  selection  that 
result  from  crowded  numbers ;  hence  the  tendency  to  disperse, 
being  self-preservative,  has  become  universal.  Some  species 
habitually  emigrate  in  prodigious  numbers :  the  African  migra- 
tory locust,  the  Rocky  JMountain  locust,  and  the  milkweed  but- 
terfly, which  annually  leaves  the  Northern  states  for  the  South 
in  immense  swarms,  in  autumn,  and  in  the  following  spring 
straggles  back  to  the  North.  Vanessa  cardiii  occasionally  mi- 
grates in  immense  numbers,  as  do  also  Picris,  some  dragon 
flies  and  some  beetles,  notably  Coccinellidje. 

Wide  Distribution  of  Insects. — Insects  have  been  found  in 
almost  every  latitude  and  altitude  explored  by  man.  Butter- 
flies and  mosquitoes  occur  beyond  the  polar  circle,  the  former 
in  Lat.  83°  N.,  the  latter  in  Lat.  y2°  N.,  and  a  species  of 
Emesa  closely  allied  to  our  common  E.  longipes  is  recorded  by 
Whymper  from  an  altitude  of  16,500  ft.  in  Ecuador,  where, 
according  to  the  same  traveler,  Orthoptera  occur  at  16,000 
ft.,  Pieris  xanthodicc  ranges  above  15,000  ft.,  and  dragon  flies. 
Hymenoptera  and  scorpions  reach  a  height  of  12,000  ft.,  while 
twenty-nine  species  of  Lepidoptera  range  upward  of  7,300 
ft.  A  ver}'  few  species  of  insects  inhabit  salt  water,  Halohatcs 
being  found  far  at  sea;  some  kinds  live  in  arid  regions  and  a 
few  even  in  hot  springs,  while  caves  furnish  many  peculiar 
species.  In  short,  insects  are  the  most  widely  distributed  of 
all  animals,  excepting  Protozoa  and  possibly  Alollusca. 

While  all  the  large  orders  of  insects  are  world-wide  in  dis- 
tribution, the  most  richly  distributed  are  Coleoptera,  Thys- 

366 


DISTRIBUTION  367 

aimra  and  C"olleml)ola,  the  last  two  feeding  usnall\'  upfMi 
minute  particles  of  organic  matter  in  the  soil  and  l)eing  remark- 
al)ly  tolerant  of  extremes  of  temperature.  The  four  chief 
families  of  butterflies  (Kcur  the  world  over,  as  do  several  fam- 
ilies of  beetles.  Of  species  that  are  essentially  cosmopolitan 
we  may  mention  the  collembolan  Isotoma  finictaria,  and  the 
butterflies  J\iucssa  canliii  and  .liiosia  plcvi/^piis,  while  among 
beetles  no  less  than  one  hundred  species  are  cosmopolitan  or 
subcosmopolitan,  including  Tcncbrio  uioUtor,  Sihainis  siiri- 
fiaiiiciisis,  Dcnncstcs  lardarius,  Atfagenns  picciis  and  Calandra 
oryrjcr.  The  coccinellid  genus  Seym  nits  occurs  in  North 
America,  Europe,  Hawaii,  Galapagos  Islands  and  New  Zea- 
land, and  A)iobiu}]i  and  Hydrobiiis  are  distributed  as  widely. 
The  huge  noctuid,  Erebus  odora,  occurring  in  Brazil  on  the 
lowlands,  and  in  Ecuador  at  an  altitude  of  10,000  ft.,  finds  its 
way  up  into  the  United  States  and  even  into  Canada.  The 
chinch  bug  and  many  other  Central  American  forms  also 
spread  far  northward,  as  described  beyond. 

Means  of  Dispersal. — This  exceptional  range  of  insects  is 
due  to  their  exceptional  natural  advantages  for  dispersal,  chief 
among  which  are  the  power  of  flight  and  the  ability  to  be 
carried  by  the  wind.  The  migratory  locust,  Schisfoccrca 
peregrina,  has  been  found  on  the  wing  five  hundred  miles  east 
of  South  America.  The  home  of  the  genus,  according  to 
Scudder,  is  Mexico  and  Central  America,  where  23  species  are 
found ;  20  occurring  in  South  America,  including  the  Gala- 
pagos Islands,  1 1  in  the  United  States  and  6  in  the  West 
Indies ;  and  there  is  every  reason  to  believe  that  5^.  peregrina 
— the  biblical  locust  and  the  only  representative  of  its  genus 
in  Africa — crossed  over  from  South  America,  where  it  is  found 
indeed  at  present.  Darwin  and  others  have  recorded  many 
instances  of  insects  being  taken  alive  far  at  sea;  Trimen  men- 
tions moths  and  longicorn  beetles  as  occurring  230  miles  west 
of  the  African  coast  and  Sphinx  convolvulus  as  flying  aboard 
ship  420  miles  out.  In  these  instances  the  insects  have  usually 
been  assisted  or  carried  by  strong'  winds,  particularly  the  trade- 


368  ENTOMOLOGY 

winds,  and  oceanic  islands  have  undonbtedly  been  colonized  in 
this  way.  On  land.  Webster  has  found  that  the  direction  in 
which  the  Hessian  fly  spreads  is  determined  largely  by  the 
prevailing  winds  at  the  time  when  these  delicate  insects  are  on 
the  wing,  and  that  the  San  Jose  scale  insect  spreads  far  more 
rapidly  with  the  prevailing  winds  than  against  them,  the  wind 
carrying  the  larvae  as  if  they  were  so  many  particles  of  dust. 
The  pernicious  buffalo-gnat  of  the  South  emerges  from  the 
waters  of  the  bayous  and  may  be  carried  on  a  strong  wind  to 
appear  suddenly  in  enormous  numbers  twenty  miles  distant 
from  its  breeding  place.  Mosquitoes  are  distributed  locally  by 
light  breezes,  but  cling  to  the  herbage  during  strong  winds. 

Ocean  currents  may  carry  eggs,  larvae  or  adults  on  vegetable 
drift  to  new  places  thousands  of  miles  away.  Thus  the  Gulf 
Stream  annually  transports  thousands  of  tropical  insects  to  the 
shores  of  Great  Britain,  where  they  do  not  survive,  however. 

Fresh-water  streams  convey  incalculable  numbers  of  insects 
in  all  stages ;  and  insects  as  a  whole  are  very  tenacious  of  life, 
being  able  to  withstand  prolonged  immersion  in  water,  and 
even  freezing,  in  many  instances,  while  they  can  live  for  a  long 
time  without  food. 

The  universal  process  of  soil-denudation  must  aid  the  dif- 
fusion of  insects,  slowly  but  constantly. 

Birds  and  mammals  disseminate  various  insects  in  one  way 
or  another,  while  the  agency  of  man  is,  of  course,  highly  im- 
portant. Intentionally,  he  has  spread  such  useful  species  as 
the  honey  bee,  the  silkworm  and  certain  useful  parasites ;  inci- 
dentally he  has  distributed  the  San  Jose  scale,  Colorado  potato 
beetle,  gypsy  moth  and  many  other  pests. 

Barriers. — The  most  important  of  the  mechanical  barriers 
which  limit  the  spread  of  terrestrial  species  is  evidently  the  sea. 
Mountain  ranges  retard  distribution  more  or  less  successfully, 
though  a  species  may  spread  along  one  side  of  a  range  and 
sooner  or  later  pass  through  a  break  or  else  around  one  end. 
Mountain  chains  act  as  barriers,  however,  chiefly  because  they 
present    unendurable    conditions    of    climate    and    vegetation. 


DISTRIBUTION  369 

For  the  same  reason  deserts  are  highly  effective  barriers.  In- 
deed the  most  important  checks  upon  distribution  are  those  of 
chmate,  and  of  chmatal  factors  temperature  is  the  most  power- 
ful. Tropical  species,  as  a  rule,  cannot  survive  and  reproduce 
in  regions  of  frost;  most  of  the  tropical  species  which  have 
entered  the  United  States  are  restricted  to  its  narrow  tropical 
belts  (PI.  4).  The  stages  of  an  insect  are  frequently  so 
accurately  adjusted  to  particular  climatal  conditions  that  an 
unfamiliar  climate  deranges  the  life  cycle.  Thus  many  South- 
ern butterflies  find  their  way  every  year  to  the  Northern  states, 
only  to  perish  w^ithout  reproducing  their  kind.  Insects,  how- 
ever, are  more  adaptable  than  most  other  animals  in  respect  to 
climate,  and  frequently  follow  their  food  plants  into  new  cli- 
mates, as  in  the  case  of  the  harlequin  cabbage  bug,  which  has 
pushed  north  from  the  tropics  to  Missouri,  southern  Illinois 
and  Indiana. 

Humidity  ranks  next  to  temperature  in  the  importance  of 
its  influence  upon  the  distribution  of  organisms,  but  in  the  case 
of  animals  acts  for  the  most  part  indirectly,  by  its  effects  upon 
vegetation.  Thus  the  effectiveness  of  an  arid  region  as  a  bar- 
rier is  due  chiefly  to  the  lack  of  vegetation  in  consequence  of 
the  lack  of  moisture.  Excessive  moisture,  on  the  other  hand, 
may  act  as  a  barrier.  The  Rocky  Mountain  locust,  migrating 
eastward  in  immense  swarms,  succumbs  in  the  moist  valley  of 
the  Mississippi ;  the  chinch  bug  is  never  seriously  injurious  in 
wet  years.  Moisture  checks  the  development  of  these  and 
other  insects  in  ways  as  yet  unascertained ;  possibly  it  acts  indi- 
rectly by  favoring  the  growth  of  fungus  diseases,  to  which 
insects  are  much  subject. 

The  absence  of  proper  food  is  more  effective  than  climate, 
as  a  direct  check  upon  the  spread  of  an  animal ;  food  itself  being, 
of  course,  dependent  ultimately  upon  climatal  factors  and  soil. 
Many  insects,  being  confined  to  a  single  food  plant,  cannot 
exist  long  where  this  plant  does  not  occur ;  but  they  will  follow 
the  plant,  as  was  just  said,  into  new  climates;  thus  Anosia 
plexippus  is  following  the  milkweed  over  the  world.  The 
25 


370  ENTOMOLOGY 

butterfly  Euphydryas  pliccton  is  remarkably  local  in  its  occur- 
rence, being  limited  to  swamps  where  its  chief  food  plant 
{Chelone  glabra)  grows;  and  Epidcmia  epixanthe  is  similarly 
restricted  to  cranberry  bogs,  though  its  food-habits  are  as  yet 
unknown. 

Former  Highways  of  Distribution. — Many  facts  of  dis- 
tribution which  are  inexplicable  under  the  present  conditions 
of  topography  and  climate  become  intelligible  in  the  light  of 
geological  history.  The  marked  similarity  between  the  fauna 
of  Europe  and  that  of  North  America  means  community  of 
origin ;  and  though  the  Arctic  zone  now  interposes  as  a  barrier, 
there  was  once  an  opportunity  for  free  dispersion  when,  in  the 
early  Pleistocene  or  late  Pliocene,  a  land  connection  existed 
between  Asia  and  North  America  and  a  warm  climate  pre- 
vailed throughout  what  is  now  the  Arctic  region. 

The  extraordinary  isolation  of  the  butterfly  CEncis  sc- 
midea  on  mountain  summits  in  New  Hampshire  and  Colo- 
rado (particularly  Mt.  Washington,  N.  H.,  and  Pike's  Peak, 
Col.)  is  explained  by  glacial  geolog}\  The  ancestors  of  this 
species,  it  is  thought,  were  driven  southward  before  an  advan- 
cing ice-sheet  and  then  followed  it  back  as  it  retreated  north- 
ward, adapted  as  they  were  to  a  rigorously  cold  climate. 
Some  of  these  ancestors  presumably  followed  the  melting  ice 
up  the  mountain  sides,  until  they  found  themselves  stranded 
on  the  summits.  Other  individuals,  undiverted  from  the  low- 
lands, followed  the  retreating  glacier  into  the  far  north ;  and 
at  present  there  occurs  throughout  Labrador  a  species  of 
GEneis  which  differs  but  slightly  from  its  lonely  ally  of  the 
mountain  tops. 

Glaciation  undoubtedly  had  a  profound  effect  upon  the 
fauna  and  flora  of  North  America.  "  With  the  slow  south- 
ward advance  of  the  ice,  animals  were  crowded  southward; 
with  its  recession  they  advanced  again  northward  to  reoccupy 
the  desolated  region,  until  now  it  has  long  been  repopulated, 
either  with  the  direct  descendants  of  its  former  inhabitants  or 
with  such  limitations  to  the  integritv  of  the  fauna  as  this  inter- 


DISTRIBUTION  371 

rnption  of  local  life  may  have  caused."  (Scudder.)  Probably 
many  species  were  exterminated  and  many  others  became 
greatly  modified,  though  little  is  known  as  to  the  relationship 
of  the  present  fauna  to  the  preglacial  fauna.  "  The  glacial 
cold  still  lingers  over  the  northern  part  of  this  continent  and 
our  present  animals  are  only  a  remnant  of  the  rich  fauna  that 
existed  in  former  ages,  when  the  magnolia  and  the  sassafras 
thrived  in  Greenland." 

Island  Faunae. — The  al)ility  of  insects  to  surmount  barriers, 
under  favorable  circumstances,  is  strikingly  shown  in  the  col- 
onization of  oceanic  islands.  Not  a  few  insects,  including 
J\incssa  carditi,  have  found  their  way  to  the  isolated  island 
of  St.  Helena.  In  the  Madeira  Islands,  according  to  Wollas- 
ton,  there  are  580  species  of  Coleoptera,  of  which  314  are 
known  to  occur  in  Europe,  wdiile  all  the  rest  are  closely  allied 
to  European  forms.  Subtracting  120  species  as  having  been 
introduced  probably  or  possibly  through  the  agency  of  man, 
there  remain  194  that  have  been  introduced  by  "  natural  " 
means.  The  rest,  266  species,  are  endemic,  though  akin  to 
European  species. 

The  scanty  insect  fauna  of  the  Galapagos  Islands  includes 
twenty  species  of  Orthoptera,  which  have  been  studied  by 
Scudder  and  by  Snodgrass.  Five  of  these  are  cosmopolitan 
cockroaches,  doubtless  introduced  commercially,  and  the  re- 
maining fifteen  are  all  "  distinctly  South  and  Central  American 
in  their  affinities."  Three  of  these  fifteen  are  strong-winged 
species  which  doubtless  arrived  by  flight  from  the  neighboring 
mainland;  indeed,  Scudder  records  a  Schistocerca  {S.  exsul) 
as  having  been  taken  at  sea  two  hundred  miles  off  the  west 
coast  of  South  America,  or  nearly  half  way  to  the  Galapagos 
Islands.  Thirteen  of  the  fifteen  are  endemic,  and  five  are 
apterous  or  subapterous,  while  a  sixth  has  an  apterous  female. 
Apterous  insects,  noticeably  common  on  wind-swept  oceanic 
islands,  may  have  been  carried  thither  on  driftwood,  though 
'i  ^s  more  likely  that  the  apterous  condition  arose  on  the 
islands,'  where  the  better-winded  and  more  venturesome  indi- 


Z72  ENTOMOLOGY 

viduals  may  have  been  constantly  swept  out  to  sea  and 
drowned,  leaving  the  more  feeble-winged  and  less  venturesome 
individuals  behind,  to  reproduce  their  own  life-saving  pecu- 
liarities. 

The  Coleoptera  of  the  Hawaiian  Islands,  studied  by  Dr. 
Sharp,  number  428  species,  representing  38  families,  and  "  are 
mostly  small  or  very  minute  insects,"  the  few  large  forms  being 
non-endemic,  with  little  or  no  doubt ;  352  species  are  at  present 
known  only  from  this  archipelago.  Dr.  Sharp  distinguishes 
three  elements  in  the  fauna :  "  First,  species  that  have  been 
introduced,  in  all  probability  comparatively  recently,  by  artifi- 
cial means,  such  as  with  provisions,  stores,  building  timber, 
ballast,  or  growing  plants ;  many  of  these  species  are  nearly 
cosmopolitan.  Second,  species  that  have  arrived  in  the  islands, 
and  have  become  more  or  less  completely  naturalized ;  they  are 
most  of  them  known  to  be  wood-  or  bark-beetles,  but  some  that 
are  not  so  may  have*  come  with  the  earth  adhering  to  the  roots 
of  floating  trees;  a  few,  such  as  the  Dytiscid?e,  or  water  beetles, 
may  possibly  have  been  introduced  by  violent  winds.  Third, 
after  making  every  allowance  for  introduction  by  these  artifi- 
cial and  natural  methods,  there  still  remains  a  large  portion 
standing  out  in  striking  contrast  with  the  others,  which  we 
are  justified  in  considering  strictly  endemic  or  autochthonous." 
Among  the  introduced  genera- are  Coccinclla,  Dcrmcstcs, 
Aphodins,  Buprestis,  Ptiniis  and  Ccrauihyx.  The  immigrant 
longicorns  appear  to  have  been  derived  "  from  the  nearest 
lands  in  various  directions  " — the  Philippine  Islands,  tropical 
America  and  the  Polynesian  Islands — and  the  same  conclusion 
will  probably  be  found  to  hold  for  the  other  immigrants,  when 
their  general  distribution  shall  have  been  sufficiently  studied. 
The  endemic  species  number  214,  or  exactly  half  the  total  num- 
ber of  species,  and  are  distributed  among  9  families,  as  follows  : 


DISTRIBUTION 

?>7Z 

Families. 

Species. 

Genera. 

Endemic  Genera. 

Carabidae, 

51 

7 

7 

Staphylinidae, 

19 

3 

I 

Nitidulidre, 

38 

2 

I 

Elatcridse, 

7 

I 

I 

Ptinidae    (Anobiini) 

19 

3 

3 

Cioidae, 

19 

I 

0 

Aglycyderidse, 

30 

I 

I 

Curculionidse 

(Cossonini),     21 

3 

3 

Cerambycidae, 

10 

I 

Sharp  writes :  "  I  think  it  may  be  looked  on  as  certain  that 
these  islands  are  the  home  of  a  large  number  of  peculiar  spe- 
cies not  at  present  existing-  elsewhere,  and  if  so  it  follows  that 
either  they  must  have  existed  formerly  elsewhere  and  migrated 
to  the  islands,  and  since  have  become  extinct  in  their  original 
homes,  or  that  they  must  have  been  produced  within  the 
islands.  This  last  seems  the  simpler  and  more  probable  sup- 
position, and  it  appears  highly  probable  that  there  has  been  a 
large  amount  of  endemic  evolution  within  the  limits  of  these 
isolated  islands." 

The  parasitic  Hymenoptera  of  Hawaii,  according  to  Ash- 
mead,  number  14  families,  69  genera  and  128  species;  only 
■eleven  genera  are  endemic  and  most  of  the  other  genera  are 
represented  in  nearly  all  the  known  faunje  of  the  earth.  Ash- 
mead  concurs  in  the  view  that  the  Hawaiian  fauna  was  origi- 
nally derived  from  the  Australasian  fauna — the  view  held  by 
all  the  specialists  who  have  studied  Hawaiian  insects. 

Geographical  Varieties. — Darwin  found  that  wide-ranging 
species  are  as  a  rule  highly  variable.  The  cosmopolitan  but- 
terfly Vanessa  cardiii  presents  striking  variations  in  different 
parts  of  the  earth,  largely  on  account  of  climatal  differences, 
as  is  indicated  by  the  temperature  experiments  of  several  inves- 
tigators. Standfuss  exposed  German  pup?e  of  this  insect  to 
cold,  and  obtained  thereby  a  dark  variety  such  as  occurs  in  Lap- 
land ;  and  by  the  influence  of  warmth,  obtained  a  very  pale  form 
such  as  occurs  normally  in  the  tropics  only.  Our  Cyaniris 
pseiidargiolus,   which   ranges   from   Alaska  into   Mexico  and 


374  ENTOMOLOGY 

from  the  Pacific  to  the  Atlantic,  exhibits  many  geographical 
varieties,  some  of  which  are  clearly  due  to  temperature,  as 
experiments  have  shown. 

Geographical  isolation  is  often  followed  by  changes  in  the 
specific  characters  of  an  organism,  as  witness  the  endemic 
species  and  varieties  of  oceanic  islands.  Even  in  the  same 
archipelago,  the  different  islands  may  be  characterized  by  dif- 
ferent varieties  of  one  and  the  same  species,  or  even  by  differ- 
ent but  closely  allied  species  of  the  same  genus.  Thus  Darwin 
and  Alexander  Agassiz  found  that  in  the  Galapagos  Islands 
each  island  had  its  own  species  of  Tropidiirus  (a  lizard)  and 
had  only  one  species,  with  almost  no  exceptions.  The  same 
phenomenon  occurs  in  the  two  Galapagan  species  of  Schisto- 
cerca — 6".  melanoccra  and  vS'.  litcrosa.  In  mclanoccra,  as 
Scudder  discovered,  "  Three  or  four  distinct  types  are  becom- 
ing gradually  differentiated  on  the  eight  [now  ten]  islands 
from  which,  they  are  known."  Snodgrass,  who  has  recently 
made  important  additions  to  Scudder's  account,  says,  in  regard 
to  the  two  species,  "  The  specimens  from  the  different  islands 
show  striking,  though,  in  most  cases,  slight  differences  distin- 
guishing the  individuals  of  each  island  as  a  race,  from  those 
inhabiting  any  other  island.  There  are  two  exceptions. 
Abingdon  and  Bindloe  have  the  same  form,  and  Albemarle 
supports  at  least  two  races."  Each  of  these  two  species  pre- 
sents no  less  than  five  racial  types,  to  which  distinctive  names 
have  been  applied.  Though  the  relationships  and  evolution  of 
these  races  have  been  ably  discussed  by  Snodgrass,  definite 
conclusions  upon  these  subjects  are  still  needed.  Isolation  in 
general  we  have  considered  briefly  in  Chapter  VII. 

Faunal  Realms. — The  general  distribution  of  life  is  such 
that  naturalists  divide  the  earth  into  several  realms,  each  of 
which  has  its  characteristic  fauna  and  flora.  As  to  the  precise 
boundaries  of  these  faunal  realms,  zoologists  do  not  all  agree, 
owing  chiefly  to  the  fact  that  faunje  overlap  one  another  to 
such  an  extent  as  to  render  their  exact  separation  more  or  less 
arbitrary.     Five   realms,   at   least,   are   generally   recognized : 


DISTRIBUTION  375 

Holarctic,    Neotropical,   Ethiopian,    Oriental    and    Australian 

(PI- 3)- 

The  Holarctic  realm  comprises  the  whole  of  Europe,  North- 
ern Africa  as  far  south  as  the  Sahara,  Asia  down  to  the  Hima- 
layas, and  North  America  down  to  Mexico.  Though  the 
fauuce  of  all  these  areas  are  fundamentally  alike  (as  Merriam 
and  other  authorities  maintain),  it  is  often  convenient  to 
divide  the  Holarctic  into  two  parts :  the  Palccarctic,  including 
Europe  and  most  of  temperate  Asia,  being  limited  roughly  by 
the  Tropic  of  Cancer;  and  the  Ncarcfic,  occupying  almost  the 
entire  continent  of  North  America,  including  Greenland.  The 
northern  portion  of  the  Holarctic  realm  forms  a  circumpolar 
l)elt  with  a  remarkable  homogeneous  fauna  and  flora ;  there- 
fore some  authors  distinguish  an  Arctic  realm,  limited  by  the 
isotherm  of  32°,  which  marks  very  closely  the  tree-limit. 

The  boreal  insects  of  Eurasia  and  North  America  are  strik- 
ingly alike.  Dr.  Hamilton  has  catalogued  nearly  six  hundred 
species  of  beetles  as  being  holarctic  in  distribution ;  five  hun- 
dred of  these  are  common  to  Europe,  Asia  and  North  America, 
and  the  remainder  are  known  to  occur  in  North  America  and 
also  in  Europe  or  Asia ;  one  hundred  are  cosmopolitan  or  sub- 
cosmopolitan,  to  be  sure,  but  fifty  of  these  are  probably  hol- 
arctic in  origin,  for  example — Dcnucstcs  lardarius  and  Tene- 
hrio  molitor.  Of  butterflies,  out  of  some  two  hundred  and 
fifty  species  that  are  found  in  the  United  States  east  of  the 
Rocky  ]\Iountains,  scarcely  more  than  a  dozen  occur  also  in 
the  old  world.  North  of  the  United  States,  however,  as 
Scudder  finds,  no  less  than  thirteen  genera  are  represented  in 
the  old  world  by  the  same  or  by  allied  species. 

The  Neotropical  realm  embraces  South  America,  Central 
America,  the  West  Indies  and  the  coasts  of  Mexico ;  Mexico 
being  for  the  most  part  a  transition  tract  between  the  Neo- 
tropical and  the  Nearctic.  The  richest  butterfly  fauna  in  the 
world  is  found  in  tropical  South  America.  To  this  region  are 
restricted,  almost  without  exception,  the  Euploeinse  and 
Lemoniinse  and  over  ninety-nine  per  cent,  of  the  Libytheinse; 


376  ENTOMOLOGY 

here  the  Hehconiiclfc  and  PapiHonidae  attain  their  highest 
development,  as  do  also  the  Cerambycid?e,  or  longicorn  beetles. 

The  Ethiopian  realm  consists  of  Africa  south  of  the  Sahara, 
Southern  Arabia  and  Madagascar ;  though  some  prefer  to 
regard  Madagascar  as  a  distinct  realm,  the  Lemiirian.  Ac- 
cording to  Wallace,  the  Ethiopian  realm  has  seventy-five  pecu- 
liar genera  of  Carabidae  and  is  marvelously  rich  in  Cetoniidse 
and  Lycaenidae. 

The  Oriental  realm  includes  India,  Ceylon,  Tropical  China, 
and  the  Western  Malay  Islands.  In  the  richness  of  its  insect 
fauna,  this  realm  vies  with  the  Neotropical.  Danaid?e  and 
Papilionidae  are  abundant,  while  the  genus  Morpho  is  repre- 
sented by  some  forty  species ;  of  Coleoptera,  Buprestidse  are 
important  and  Lucanidse  especially  so. 

The  Australian  realm  embodies  Australia,  New  Zealand,  the 
Eastern  Malay  Islands  and  Polynesia.  Buprestidae  are  here 
represented  by  forty-seven  genera,  of  which  twenty  are  pecu- 
liar; against  this  showing,  the  Oriental  has  forty-one  genera 
and  the  Neotropical  thirty-nine  (W^allace).  Strong  affinities 
are  said  to  exist  between  the  Australian  and  Neotropical  insect 
faunae. 

Life  Zones  of  North  America. — Merriam,  the  chief  au- 
thority upon  the  subject,  says :  *'  The  continent  of  North 
America  may  be  divided,  according  to  the  distribution  of  its 
animals  and  plants,  into  three  primary  transcontinental  regions 
— Boreal,  Austral  and  Tropical."      (PI.  4.) 

The  Boreal  region  covers  the  northern  part  of  the  continent 
to  about  the  northern  boundary  of  the  United  States  and  con- 
tinues southward  along  the  higher  portions  of  the  mountain 
ranges.  This  region  is  divided  into  three  transcontinental 
zones:  (i)  the  Arctic- Alpine,  lying  above  the  limits  of  tree 
growth,  in  latitude  or  altitude;  (2)  the  Hudsonian,  compris- 
ing the  northern  part  of  the  great  transcontinental  coniferous 
forest  and  the  upper  timbered  slopes  of  the  highest  mountains 
of  the  United  States  and  Mexico;  (3)  the  Canadian,  covering 
the  remainder  of  the  Boreal  region.  The  butterfly  Erynnis 
manitoha  (Fig.  292)  is  strictly  boreal  in  distribution. 


DISTRIBUTION 


377 


The  Austral  region  "  covers  the  \\h()le  of  the  United  States 
and  Mexico,  except  the  Boreal  mountains  and  tlie  TroiMcal 
lowlands."  It  comprises  three  transcontinental  l)elts :  (i)  the 
Transition  zone,  in  which  the  Boreal  and  the  Austral  overlap; 
(2)  the  Upper  Austral;  (3)  tha  LoK'cr  Austral.     The  butter- 


FlG.    202. 


P'lG.    293. 


"TP^g^ 

n— tm35C 

vA 

^)3S^ 

^\\ 

\/^^      \) 

Distribution  of  Erynnis  manitoba,  a 
butterfly  restricted  to  subarctic  and  sub- 
alpine  regions. — After   Scudder. 


Distribution  in  the  United  States  of 
Etidamits  protciis,  primarily  a  tropical 
butterfly. — After   Scudder. 


tiy  Eudainus  protcus  (Fig.  293)  is  restricted,  generally  speak- 
ing, to  the  Tropical  region  and  the  warmer  and  more  humid 
portions  of  the  Austral. 

The  Tropical  region  covers  the  southern  extremity  of 
Florida  and  of  Lower  CaHfornia,  most  of  Central  America  and 
a  narrow  strip  along  the  two  coasts  of  Mexico,  the  western 
strip  extending  up  into  California  and  Arizona. 

These  divisions  are  based  primarily  upon  the  distribution  of 
mammals,  birds  and  plants,  and  the  three  primary  divisions 
serve  almost  equally  well  for  insects  also.  In  regard  to  the 
zones,  however^  not  so  much  can  be  said — for  insects  are  to  a 
high  degree  independent  of  minor  differences  of  climate. 
Many  instances  of  this  are  given  beyond. 

The  insect  fauna  of  the  United  States  is  upon  the  whole  a 
heterogeneous  assemblage  of  species  derived  from  several 
sources,  and  the  foreign  element  of  this  fauna  we  shall  con- 
sider at  some  length. 

Paths  of  Diffusion  in  North  America. — It  may  be  laid 
down  as  a  general  rule  that  every  species  tends  to  spread  in 


3/8  ENTOMOLOGY 

all  directions  and  does  so  spread  until  its  further  progress  is 
prevented,  in  one  way  or  another.  The  paths  along  which  a 
species  spreads  are  determined,  then,  by  the  absence  of  barri- 
ers. The  diffusion  of  insects  in  our  own  country  has  received 
much  attention  from  entomologists,  especially  in  the  case  of 
such  insects  as  are  important  from  an  economic  standpoint. 
The  accessions  to  our  insect  fauna  have  arrived  chiefly  from 
Asia,  Central  and  South  America,  and  Europe. 

Webster,  our  foremost  student  of  this  subject,  to  whom  the 
author  is  indebted  for  most  of  his  facts,  names  four  paths  along 
which  insects  have  made  their  way  into  the  United  States : 
( I )  Northwest — Northern  Asia  into  Alaska  and  thence  south 
and  east;  (2)  Southwest — Central  America  through  Mexico; 
(3)  Southeast — AVest  Indies  into  Florida;  (4)  Eastern — from 
Europe,  commercially. 

Northwest.  —  The  northern  parts  of  Europe,  Asia  and 
North  America  have  in  common  very  many  identical  or  closely 
allied  species,  whose  distribution  is  accounted  for  if,  as  geol- 
ogists assure  us,  Asia  and  North  America  were  once  con- 
nected, at  a  time  when  a  subtropical  climate  prevailed  within 
the  Arctic  Circle;  in  fact,  the  distribution  is  scarcely  explic- 
able upon  any  other  theory.  Curiously  enough,  the  trend  of 
diffusion  seems  to  have  been  from  Asia  into  North  America 
and  rarely  the  reverse,  so  far  as  can  be  inferred. 

Coccinella  qninquenotata,  occurring  in  Siberia  and  Alaska, 
has  spread  to  Hudson  Bay,  Greenland,  Kansas,  Utah,  Califor- 
nia and  Mexico ;  while  C.  sanguinea,  well  known  in  Europe 
and  Asia,  ranges  from  Alaska  to  Patagonia ;  and  Megilla  iiiac- 
ulata  from  Vancouver  and  Canada  to  Chile.  About  six  hun- 
dred species  of  beetles  are  holarctic  in  distribution,  as  was 
mentioned.  Some  of  them  inhabit  different  climatal  regions 
in  different  parts  of  their  range;  thus  Melasoma  (Lina)  lap- 
pon'iea  in  the  Old  World  "  occurs  only  in  the  high  north  and 
on  high  mountain  ranges,  whereas  in  North  America  it  ex- 
tends to  the  extreme  southern  portion  of  the  country,"  being 
widely    diffused    over    the    lowlands    (Schwarz).      Similarly, 


DISTRIBUTION  379 

Silpha  lappoiiica  is  strictly  arctic  in  Europe,  but  is  distrilmted 
over  mi^st  of  North  America;  Silpha  opaca,  on  the  contrary, 
is  common  all  over  Europe,  but  is  strictly  arctic  in  North 
America.  Silplia  atrata,  common  throug-hout  Europe  and 
western  Siberia,  was  introduced  into  North  America,  but  failed 
to  establish  itself. 

Southwest. — \>ry  many  species  have  come  to  us  from  Cen- 
tral America  and  even  from  South  America.  South  America 
appears  to  be  the  home  of  the  genus  Halisidota,  according  to 
Webster,  who  has  traced  several  of  our  North  American  spe- 
cies as  offshoots  of  South  American  forms.  Many  of  our 
species  may  be  traced  back  to  Yucatan.  //.  ciiictipcs  ranges 
from  South  America  to  Texas  and  Elorida ;  H.  tcsscUaris  has 
spread  northward  from  Central  America  and  now  occurs  over 
the  middle  and  eastern  United  States,  while  a  form  closely  like 
fesscllaris  ranges  from  Argentina  to  Costa  Rica ;  H.  carycc 
follows  tessellaris,  and  appears  to  have  branched  in  Central 
America,  giving  ofif  H.  agassizii,  which  extends  northward 
into  California.  Similarly  in  the  case  of  the  Colorado  potato 
beetle  {Lcpuuotavsa  dcccinUncata)  and  its  relatives.  Accord- 
ing to  Tower,  the  parent  form,  L.  undcccuiUncata,  seems  to 
have  arisen  in  the  northern  part  of  South  America,  to  have 
migrated  northward  and,  in  the  diversified  Mexican  region,  to 
have  split  into  several  racial  varieties.  The  parent  form 
grades  into  L.  mnltiUncata  of  the  Mexican  table  lands,  which 
in  turn,  in  the  northern  part  of  the  Mexican  plateau,  passes 
imperceptibly  into  L.  dcccmlincata,  which  last  species  has 
spread  northward  along  the  eastern  slope  of  the  western  high- 
lands, west  of  the  arid  region.  In  the  lower  part  of  the  Mex- 
ican region  the  parent  form  may  be  traced  into  L.  juncta, 
which  has  spread  along  the  low  humid  Gulf  Coast,  up  the  Miss- 
issippi valley  to  southern  Illinois,  and  along  the  Gulf  Coast 
and  up  the  Atlantic  coast  to  Maryland,  Delaware  and  New 
Jersey.  In  general,  the  mountains  of  Central  America  and 
Mexico  and  the  plateau  of  Mexico  have  been  barriers  to  the 
northward  spread  of  many  species,  which  have  reached  the 


380  ENTOMOLOGY 

United  States  by  passing  to  the  east  or  to  the  west  of  these 
barriers,  in  the  former  case  skirting  the  Gulf  of  Mexico  and 
spreading  northward  along  the  Mississippi  valley  or  along  the 
Atlantic  coast,  in  the  latter  event  traveling  along  the  Pacific 
coast  to  California  and  other  Western  states.  Not  a  few  spe- 
cies, however,  have  made  their  way  from  the  Mexican  plateau 
into  New  Mexico  and  Arizona ;  this  is  true  of  many  Sphin- 
gidas.  The  butterfly  Anosia  herenice  ranges  from  South 
America  into  New  Mexico,  Arizona  and  Colorado ;  while  many 
of  the  Libytheidae  have  entered  Arizona  and  neighboring  states 
from  Mexico.  The  chrysomelid  genus  Diabrotica  is  almost 
exclusively  confined  to  the  western  hemisphere  and  its  home 
is  clearly  in  South  America,  where  no  less  than  367  species  are 
found.  About  100  species  occur  in  Venezuela  and  Colombia, 
"  of  which  1 1  extend  into  Guatemala,  8  into  Mexico,  and  i 
into  the  United  States."  We  have  18  species  of  Diabrotica, 
almost  all  of  which  can  be  traced  back  to  Mexico,  and  several 
of  them — as  the  common  D.  longicornis — to  Central  America. 
"  The  common  Dyiiasfcs  fityus  occurs  from  Brazil  through 
Central  America  and  Mexico,  and  in  the  United  States  from 
Texas  to  Illinois  and  east  to  southern  New  York  and  New 
England."  Erebus  odora  ranges  from  Ecuador  and  Brazil  to 
Colorado,  Illinois,  Ohio,  New  England  and  into  Canada, 
though  it  is  not  known  to  breed  in  North  America,  being  in 
fact  a  rare  visitor  in  our  northern  states. 

Southeast. — Many  South  American  species  have  made  their 
way  into  southern  and  western  Florida  by  way  of  the  West 
Indies,  while  some  subtropical  species  have  reached  Florida 
probably  by  following  around  the  Gulf  coast.  The  semi- 
tropical  insect  fauna  of  southern  and  southwestern  Florida, 
including  about  300  specimens  of  Coleoptera,  according  to 
Schwarz,  is  entirely  of  West  Indian  and  Central  American 
origin,  the  species  having  been  introduced  with  their  food 
plants,  chiefly  by  the  Gulf  Stream,  but  also  by  flight,  as  in  the 
case  of  Sphingidse.  Ninety-five  species  of  Hemiptera  collected 
in  extreme  southern  Florida  by  Schwarz  and  studied  by  Uhler 


DISTRIBUTION  38 1 

are  distinctly  Central  American  and  West  Indian  in  their 
affinities.  Indeed  Uhler  is  inclined  to  believe  that  the  principal 
portion  of  the  Ilemiptera  of  the  United  States  has  been  derived 
from  the  region  of  Central  America  and  Mexico. 

Eastern. — On  the  Atlantic  coast  are  many  European  species 
of  insects  which  ha^•e  arri\-ed  throug'h  the  ag-encv  of  man. 
Most  of  them  have  not  as  }et  passed  the  Appalachian  moun- 
tain system,  but  some  have  worked  their  way  inland.  Thus 
the  common  cabbage  butterfly  (Pieris  rapcc),  first  noticed  in 
Quebec  about  i860,  was  found  in  the  northern  parts  of  Maine, 
New  Hampshire  and  Vermont  five  or  six  years  later,  was 
established  in  those  states  by  1867,  entered  New  York  in  1868 
and  then  Ohio.  Aphodius  fossor  followed  much  the  same 
course  from  New  York  into  northeastern  Ohio,  as  did  also  the 
asparagus  beetle  (Crioccris  asparagi),  the  clover  leaf  weevil 
(PhytoJionins  puncfatiis) ,  the  clover  root  borer  (Hylostcs 
ohscurus)  and  other  species.  In  short,  as  Webster  has  pointed 
out.  New  York  offers  a  natural  g'ateway  through  which  species 
introduced  from  Europe  spread  westward,  passing  either  to  the 
north  or  to  the  south  of  Lake  Erie. 

Inland  Distribution. — Pieris  rapcc,  the  spread  of  which  in 
North  America  has  been  thoroughly  traced  by  Scudder, 
reached  northern  New  York  in  1868  (as  above),  but  appears 
to  have  been  independently  introduced  into  New^  Jersey  in 
1868,  whence  it  reached  eastern  New  York  again  in  1870;  it 
was  seen  in  northeastern  Ohio  in  1873,  Chicago  1875,  Iowa 
1878,  Minnesota  1880,  Colorado  1886,  and  has  extended  as 
far  south  as  northern  Florida,  but  is  apparently  unable  to  make 
its  way  down  into  the  peninsula. 

Crioccris  asparagi,  another  native  of  Europe,  became  con- 
spicuous in  Long  Island  in  1856,  spread  southward  to  Virginia 
and  westward  to  Ohio,  where  it  was  taken  in  1886;  it  occurs 
now  in  Illinois.  This  insect,  as  Howard  observes,  flies  read- 
ily, and  may  be  introduced  commercially  in  the  egg  or  larval 
stage  on  bunches  of  asparagus. 

Cryptorhyiichits  hipatJii,  a  beetle  destructive  to  willows  and 


382  ENTOMOLOGY 

poplars,  and  common  in  Europe,  Siberia  and  Japan,  was  found 
in  New  Jersey  in  1882  and  in  New  York  in  1896,  though 
known  for  many  years  previously  in  Massachusetts.  It  be- 
came noticeable  in  Ohio  in  1901,  and  is  steadily  extending  its 
ravages,  being  reported  recently  from  Minnesota. 

From  Colorado  the  well-known  potato  beetle  (Leptinotarsa 
dcccinUncata)  has  worked  eastward  since  1840,  reaching  the 
Atlantic  coast  within  twenty  years,  and  has  even  made  its  way 
several  times  into  Great  Britain,  only  to  be  stamped  out  with 
commendable  energy.  The  box-elder  bug  (Leptocoris  trk'it- 
tatiis)  is  similarly  working  eastward,  having  now  reached 
Indiana.  The  Rocky  Mountain  locust  periodically  migrates 
eastward,  but  meets  a  check  in  the  moist  valley  of  the  Missis- 
sippi, as  has  been  said. 

The  chinch  bug  (Blissiis  leucopterus),  the  distribution  of 
which  has  been  traced  by  Webster,  has  spread  from  Central 
America  and  Mexico  northward  along  the  Gulf  coast  into  the 
United  States,  following  three  paths:  (i)  Along  the  Atlantic 
coast  to  Cape  Breton;  (2)  along  the  Mississippi  valley  and 
northward  into  Manitoba;  (3)  along  the  western  coast  of  Cen- 
tral America  and  Mexico  into  California  and  other  Western 
states.  Everywhere  this  insect  has  found  wild  grasses  upon 
which  to  feed,  but  has  readily  forsaken  these  for  cultivated 
grasses  upon  occasion.  The  harlequin  cabbage  bug  {Murgan- 
tia  hisfrionica)  has  spread  from  Central  America  into  Califor- 
nia and  Nevada,  and  has  steadily  progressed  in  the  Mississippi 
basin  as  far  north  as  Illinois,  Indiana  and  Ohio,  though  it 
appears  to  be  unable  to  maintain  itself  in  the  northern  parts 
of  these  states.  This  insect  required  about  twenty-five  years 
to  pass  from  Louisiana  (1864)  to  Ohio,  spreading  through  its 
own  efforts  and  not  commercially  to  any  great  extent. 

Every  year  some  of  the  southern  butterflies  reach  the  North- 
ern states,  where  they  die  without  finding  a  food  plant,  or  else 
maintain  a  precarious  existence.  Thus  Iphiclides  ajax  occa- 
sionally reaches  Massachusetts  as  a  visitor  and  a  visitor  only ; 
Lccrtias  philcnor,  however,  finds  a  limited  amount  of  food  in 


DISTRIBUTION  383 

the  cultivated  ArisfolocJiia.  P.  tlioas,  one  of  the  pests  of 
the  orange  tree  in  the  South,  is  highly  prized  as  a  rarity  by 
New  England  collectors  and  is  able  to  perpetuate  itself  in  the 
Middle  States  on  the  prickly  ash  (Xaiithoxyluin).  The 
strong-winged  grasshopper,  Schistocerca  amcricana,  l)elonging 
to  a  genus  the  center  of  whose  dispersion  is  tropical  America, 
ranges  freely  over  the  interior  of  North  America,  sometimes 
in  great  swarms,  and  its  nymphs  are  able  to  survive  in  mode- 
rate numbers  in  the  southern  parts  of  Illinois,  Ohio  and  other 
states  of  as  high  latitude,  while  the  adults  occasionally  reach 
Ontario,  Canada. 

Many  species  are  now  so  widely  distributed  that  their  for- 
mer paths  of  ditifusion  can  no  longer  be  ascertained.  The 
army  worm  {Hcliopliila  unipiiiicta) ,  feeding  on  grasses,  and 
occurring  all  over  the  United  States  south  of  Lat.  44°  N.,  is 
found  also  in  Central  America,  throughout  South  America, 
and  in  Europe,  Africa,  Japan,  China,  India,  etc. ;  in  short,  it 
occurs  in  all  except  the  coldest  parts  of  the  earth,  and  where 
it  originated  no  one  knows. 

Determination  of  Centers  of  Dispersal. — In  accounting 
for  the  present  distribution  of  life,  naturalists  employ  several 
kinds  of  evidence.  Adams  recognizes  ten  criteria,  aside  from 
palaeontological  evidence,  for  determining  centers  of  dispersal : 

1.  Location  of  greatest  differentiation  of  a  type. 

2.  Location  of  dominance  or  great  abundance  of  individuals. 

3.  Location  of  S3mthetic  or  closely  related  forms  (Allen). 

4.  Location  of  maximum  size  of  individuals  (Ridgway- 
Allen). 

5.  Location  of  greatest  productiveness  and  its  relative  sta- 
bility, in  crops  (Hyde). 

6.  Continuity  and  convergence  of  lines  of  dispersal. 

7.  Location  of  least  dependence  upon  a  restricted  habitat. 

8.  Continuity  and  directness  of  individual  variations  or 
modifications  radiatine  from  the  center  of  oriein  alone:  the 


gn 


highways  of  dispersal. 

9.  Direction  indicated  by  biogeographical  affinities. 


3^4  ENTOMOLOGY 

lo.  Direction  indicated  by  the  annual  migration  routes,  in 
birds  (Palmen). 

2.  Geological 

Means  of  Fossilization. — Abundant  as  insects  are  at  pres- 
ent, they  are  comparatively  rare  as  fossils,  the  fossil  species 
forming  but  one  per  cent,  of  the  total  number  of  described 
species  of  insects.  The  absence  of  insect  remains  in  sedimen- 
tary rocks  of  marine  origin  is  explained  by  the  fact  that  almost 
no  insects  inhabit  salt  water ;  and  terrestrial  forms  in  general 
are  ill-adapted  for  fossilization.  The  hosts  of  insects  that  die 
each  year  leave  remarkably  few  traces  in  the  soil,  owing  per- 
haps, in  great  measure,  to  the  dissolution  of  chitin  in  the  pres- 
ence of  moisture. 

]\Iost  of  the  fossil  insects  that  are  known  have  been  found 
in-  vegetable  accumulations  such  as  coal,  peat  and  lignite,  or 
else  in  ancient  fresh-water  basins,  where  the  insects  were  prob- 
ably drowned  and  rapidly  imbedded.  At  present,  enormous 
numbers  of  insects  are  sometimes  cast  upon  the  shores  of  our 
great  lakes — a  phenomenon  which  helps  to  explain  the  profu- 
sion of  fossil  forms  found  in  some  of  the  ancient  lake  basins. 

Insects  in  rich  variety  have  been  preserved  in  amber,  the 
fossilized  resin  of  coniferous  trees.  This  substance,  as  it 
exuded,  must  have  entangled  and  enveloped  insect  visitors  just 
as  it  does  at  present.  ]\Iany  of  these  amber  insects  are  ex- 
cjuisitely  preserved,  as  if  sealed  in  glass.  Copal,  a  transparent, 
amber-like  resin  from  various  tropical  trees,  particularly  Legu- 
minosje,  has  also  yielded  many  interesting  insects. 

Ill-adapted  as  insects  are  by  organization  and  habit  for  the 
commoner  methods  of  fossilization,  the  number  of  fossil  spe- 
cies already  described  is  no  less  than  three  thousand. 

Localities  for  Fossil  Insects. — The  Devonian  of  New 
Brunswick  has  furnished  a  few  forms,  found  near  St.  John,  in 
a  small  ledge  that  outcrops  between  tide-marks ;  these  forms, 
though  few,  are  of  extraordinary  interest,  as  will  be  seen. 

For  Carboniferous  species,  Commentry  in  France  is  a  noted 
locality,  through  the  admirable  researches  of  Brongniart,  who 


DISTRIBUTION 


385 


Fig, 


descriljed  from  there  97  species  of  48  genera,  representing-  12 
families  or  higher  groups,  lo  of  which  are  regarded  as  extinct; 
without  including  many  hundred  specimens  of  cockroaches 
which  he  found  hut  did  not  study.  In  this  country,  many 
species  have  heen  found  in  the  coal  fields  of  Illinois,  Nova 
Scotia,  Rhode  Island,  Pennsylvania  and  Ohio. 

Many  fine  fossils  of  the  Jurassic  period  have  heen  found  in 
the  lithographic  limestones  of  Bavaria;  143  species  from  the 
Lias — four  fifths  of  them  heetles — were  studied  hy  Heer. 

The  Tertiary  period  has  furnished  the  majority  of  fossil 
specimens.  To  the  Oligocene  helong  the  amher  insects,  of 
which  900  species  are  known  from  Baltic  amber  alone,  and  to 
the  same  epoch  are  ascribed  the  deposits  of  Florissant  and 
White  River  in  Colorado  and  of  Green  River,  Wyoming. 
These  localities — the  richest  in  the  world — have  been  made 
famous  by  the  monumental  works  of  Scudder.  At  Florissant 
there  is  an  extinct  lake,  in  the  bed  of 
which,  entombed  in  shales  derived 
from  volcanic  sand  and  ash,  the  re- 
mains of  insects  are  found  in  aston- 
ishing profusion.  For  Miocene 
forms,  of  which  1,550  European  spe- 
cies are  known,  the  CEningen  beds  of 
Bavaria  are  celebrated  as  having  furnished  844  species,  des- 
cribed by  the  illustrious  Heer. 

Pleistocene  species  are  supplied  by  the  peats  of  France  and 
Europe,  the  lignites  of  Bavaria,  and  the  interglacial  clays  of 
Switzerland  and  Ontario,  Canada. 

Silurian  and  Devonian, — The  oldest  fossil  insect  known 
consists  of  a  single  hemipterous  wing,  Protociiiic.v,  from  the 
Lower  Silurian  of  Sweden.  Next  in  age  comes  a  wing, 
Palcuoblaffiiia  (Fig.  294),  of  doubtful  position,^  from  the 
Middle  Silurian  of  France.  Following  these  are  six  speci- 
mens of  as  many  remarkable  species  from  the  Devonian  shales 

^  There  is  some  evidence,  it   should  be   said,  that  this   species  is  not  an 
insect.     Handhrsch  denies  also  that  Protocimcx  is  an   insect. 


Palccohlattina  douvillci,  iiatur 
size. — After    Brongniart. 


386 


ENTOMOLOGY 


of  New  Brunswick.  The  specimens,  to  be  sure,  are  nothing- 
but  broken  wings,  yet  these  few  fragments,  interpreted  by  Dr. 
Scuckler.  are  rich  in  meaning.  All  are  neuropteroid,  but  they 
cannot  be  classified  satisfactorily  with  recent  forms  on  account 

Fig.  295. 


Platcpl 


\fter  ScuDDER. 


of  being"  highly  synthetic  in  structure.  Thus  Platcphciiicra 
aiitiqiia  (Fig.  295).  though  essentially  a  May  fly  of  gigantic 
proportions  (spreading  probably  135  mm.),  has  an  odonate 
type  of  reticulation;  while  Xcnoncum  (Fig.  296)  combines 
characters  which  are  now  distributed  among  Ephemeridse, 
Sialidje.  Rhaphidiidae,  Coniopterygid?e,  and  other  families, 
besides  being  in  many  respects  unique.     These  Devonian  forms 


Xenoneura  antiquornm,  five  times 


After  ScuDDER. 


attained  huge  dimensions  as  compared  with  their  recent  repre- 
sentatives;  Gcrcphcincra,  for  example,  had  an  estimated  ex- 
panse of  175  millimeters. 

Carboniferous. — The  Carboniferous  age,  with  its  luxuriant 
vegetation,  is  marked  by  the  appearance  of  insects  in  great 


DISTRIBUTION 


387 


number  and  variety,  still  restricted,  however,  to  the  more 
generalized  orders.  The  dominance  of  cockroaches  in  the 
Carboniferous  is  especially  noteworthy,  no  less  than  200  Palcco- 
zoic  species  being-  known  from  Eu- 
rope and  North  America.  These  ''  "'^''' 
ancient  roaches  (Fig.  297)  differed 
from  their  modern  descendants  in 
the  similarity  of  the  two  pairs  of 
wings,  which  were  alike  in  form. 
size,  transparency  and  g-eneral  neu- 
ration.  with  six  principal  ner\-ures 
in  each  wing;  while  in  recent  cock- 
roaches the  front  wings  have  be- 
come tegmina,  with  certain  of  the 
veins  always  blended  together, 
though  the  hind  wings  have  retained 
their  primitive  characteristics  with  a 
few  modifications,  such  as  the  ex- 
pansion of  the  anal  area.  Car- 
boniferous cockroaches  furthermore 
exhibit  ovipositors,  straight,  slender, 
and  half  as  long  again  as  the  abdo- 
men— organs  which  do  not  exist  in 
recent  species. 

Lithomantis  (Fig.  298),  a  remarkable  form  from  Scotland, 
possessed  in  addition  to  its  four  large  neuropteroid  wings, 
a  pair  of  prothoracic  wing-like  appendages  which,  provided 
they  may  be  regarded'  as  homologous  with  wings,  represent 
a  third  pair,  either  atrophied  or  undeveloped — a  condition 
which  is  never  found  today,  unless  the  patagia  of  Lepidoptera 
represent  wings,  which  is  unlikely. 

From  the  rich  deposits  of  Commentry,  Brongniart  has  des- 
cribed several  forms  of  striking  interest.  Dictyoneura  is  a  Car- 
boniferous genus  with  neuropteroid  wings  and  an  orthopteroid 
body,  having,  in  common  with  several  contemporary  genera, 
strong  isopteran  affinities.     Corydaloides  scudderi,  a  phasmid, 


Efoblattina  ma::ona,  a  Car- 
boniferous cockroach  from 
Illinois.  Twice  natural  size. 
— After  ScuDDER  in  Miall  and 
Denny. 


388 


ENTOMOLOGY 


has  an  alar  expanse  of  twenty-eight  inches.  The  Carbonife- 
rons  prototypes  of  oiir  Odonata  were  gigantic  l3eside  their 
modern  descendants,  one  of  them  (il/t^o^a;/c'//;77 )  having  a  spread 
of  over  two  feet ;  they  were  more  generahzed  in  strnctnre  than 
recent  Odonata,  presenting  a  much  simpler  type  of  neuration 
and  less  differentiation  of  the  segments  of  the  thorax.  The 
Carboniferous   precursors   of  our   May   flies   attained   a   high 

Fig.  298. 


Lithomantis  carbonarius,   showing  prothoracic   appendages.     Two   thirds   natural    size.- 
After  WooDW.\RD. 


development  in  number  and  variety ;  in  fact,  the  Ephemeridse, 
like  the  Blattidse,  achieved  their  maximum  development  ages 
ago,  wdien  they  attained  an  importance  strongly  contrasting 
with  their  present  meager  representation. 

The  Permian  has  supplied  a  remarkable  genus  Eugcrcon 
(Fig.  299)  with  hemipterous  mouth  parts  associated  with  fili- 
form antennae  and  orthopteroid  wings.  The  earliest  uncjues- 
tionable  traces  of  insects  with  an  indirect  metamorphosis  are 
found  in  the  Permian  of  Bohemia,  in  the  shape  of  caddis  worm 
cases. 

Triassic. — Triassic  cockroaches  present  interesting  stages 
in  the  evolution  of  their   familv.     Through   these   ]\Iesozoic 


DISTRIBUTION 


389 


Species,  the  continuity  between  Paheozoic  and  recent  cock- 
roaches is  clearly  established — which  can  be  said  of  no  other 
insects ;  and  in  fact  of  no  other  animals,  the  only  comparable 
cases  being  those  of  the  horse  and  the  molluscan  oenus  Planor- 
his.     In  the  Triassic  period  occur  the  first  fossils  that  can  be 


Fig 


Eiigcrcon  bockingi.     Three  quarter 


size. — After   Dohrn. 


referred  indisputably  to  Coleoptera  and  Hymenoptera,  the  lat- 
ter order  being  represented  first,  as  it  happens,  by  some  of 
its  most  specialized  members,  namely  ants. 

Jurassic. — At  length,  in  the  Jurassic,  all  the  large  orders 
except  Lepidoptera  occur;  Diptera  appear  for  the  first  time, 
and  Odonata  are  represented  by  many  well-preserved  speci- 
mens, while  the  Liassic  Coleoptera  studied  by  Heer  number 
over  one  hundred  species.  The  Cretaceous  has  yielded  but 
few^  insects,  as  might  be  expected. 

Tertiary. — In  the  rich  Tertiary  deposits  all  orders  of  insects 
occur.  Baltic  amber  has  yielded  Collembola,  some  remarkable 
Psocidae,  many  Diptera,  and  ants  in  abundance.     Of  844  spe- 


390 


ENTOMOLOGY 


cies  taken  from  the  noted  Miocene  beds  of  CEning-en,  nearly 
one  half  were  Coleoptera,  followed  by  neuropteroid  forms 
(seventeen  per  cent.)  and  Hymenoptera  (fourteen  per  cent.)  ; 
ants  were  twice  as  numerous  in  species  as  they  are  at  present 
in  Europe.  Almost  half  the  known  species  of  fossil  insects 
have  been  described  from  the  Miocene  of  Europe.  To  the 
Miocene  belongs  the  indusial  limestone  of  Auvergne,  France, 
where  extensive  beds — in  some  places  two  or  three  meters 
deep — consist  for  the  most  part  of  the  calcified  larval  cases  of 
caddis  flies. 

At  Florissant,  as  contrasted  with  CEningen  by  Scudder, 
Hymenoptera  constitute  40  per  cent,  of  the  specimens,  owing 
chiefly  to  the  predominance  of  ants ;  Diptera  follow  with  30 
per  cent,  and  then  Coleoptera  with  13  per  cent.  Modern  fam- 
ilies are  represented  in  great  profusion.  The  material  from 
Florissant  and  neighboring  localities  includes  a  Lcpisina,  fif- 
teen species  of  Psocidae,  over  thirty  species  of  x\phididae,  and 
over  one  hundred  species  of  Elateridse,  while  the  Rhynchoph- 
ora    number    193    species    as    against  150    species    from    the 

Tertiary  of  Europe.  Tipu- 
lidas  are  abundant  and  ex- 
cjuisitely  preserved,  while 
Bibionidae,  as  compared  with 
their  present  numbers,  are 
surprisingly  common.  Nu- 
merous masses  of  eggs  oc- 
cur, undoubtedly  sialid  and 
closely  like  those  of  Cory- 
dalis.  Sialid  characters,  in- 
deed, appear  in  the  oldest 
fossils  known,  and  are 
strongly  manifest  through- 
out the  fossil  series,  though  among  recent  insects  Sialidce  oc- 
cupy only  a  subordinate  place.  Strange  to  say,  few'  aquatic 
insects  have  been  found  in  this  ancient  lake  basin. 

Fossil  butterflies  are  among  the  greatest  rarities,  only  sev- 


Proclyyas  pcrscphonc,  a  fossil  butterfly 
from  Colorado.  Natural  size.  — •  After 
Scudder. 


DISTRIBUTION  .  39I 

enteen  being  known  :  yet  Florissant  has  contributed  eight  of 
these,  a  few  of  which  are  marvelOusly  well  preserved  (Fig. 
300),  as  appears  from  Scudder's  figures.  Two  of  the  Floris- 
sant specimens  belong  to  Libytheinse,  a  group  now  scantily 
represented,  though  widely  distributed  over  the  earth.  The 
group  is  structurally  an  archaic  one.  and  its  recent  members 
(forming  only  one  eight-hundredth  of  the  described  species 
of  butterfiies)  are  doubtless  relicts. 

Taken  as  a  whole,  the  insect  facies  of  Tertiary  times  was 
apparently  much  the  same  as  at  present.  The  Florissant  fauna 
and  flora  indicate,  however,  a  former  climate  in  Colorado  as 
warm  as  the  present  climate  of  Georgia. 

Quaternary. — The  interglacial  clays  of  Toronto,  Ontario, 
have  yielded  fragments  of  the  skeletons  of  beetles  to  the  extent 
of  several  hundred  specimens,  about  one  third  of  which 
(chiefly  eilytra)  were  sufiiciently  complete  or  characteristic  to 
be  identified  by  Dr.  Scudder,  who  has  found  in  all  76  species 
of  beetles,  representing  8  families,  chiefly  Carabido;  and 
Staphylinidse.  All  these  interglacial  beetles  are  referable  to 
recent  genera,  but  none  of  them  to  recent  species,  though  the 
differences  between  the  interglacial  species  and  their  recent 
allies  are  very  slight.  As  a  whole,  these  species  "  indicate 
a  climate  closely  resembling  that  of  Ontario  to-day,  or  perhaps 
a  slightly  colder  one.  .  .  .  One  cannot  fail,  also,  to  notice  that 
a  large  number  of  the  allies  of  the  interglacial  forms  are  re- 
corded from  the  Pacific  coast."  (Scudder.)  The  writer,  who 
has  studied  these  specimens,  has  been  impressed  most  by  their 
likeness  to  modern  species.  It  is  indeed  remarkable  that  so 
little  specific  differentiation  has  occurred  in  these  beetles  since 
the  interglacial  epoch — certainly  ten  thousand  and  possibly 
two  or  three  hundred  thousand  years  ago. 

General  Conclusions. — Unfortunately,  the  earliest  fossils 
with  which  we  are  acquainted  shed  much  less  light  upon  the 
subject  of  insect  phylogeny  than  one  might  expect.  The  few 
Devonian  forms,  though  synthetic  indeed  as  compared  with 
their  modern  allies,  are  at  the  same  time  highly  organized,  or 


392  ENTOMOLOGY 

far  from  primitive,  and  their  ancestors  have  been  obhterated. 

The  general  plan  of  wing-  structure,  as  Scudder  finds,  has 
remained  unaltered  from  the  earliest  times,  though  the  De- 
vonian specimens  exhibit  many  peculiarities  of  venation,  in 
which  respect  some  of  them  are  more  specialized  than  their 
nearest  living  allies,  while  none  of  them  have  much  special 
relation  to  Carboniferous  forms. 

Carboniferous  insects  are  more  nearly  related  to  recent 
forms  than  are  the  Devonian  species,  but  present  a  number  of 
significant  generalized  features.  Generally  speaking,  the  tho- 
racic segments  were  similar  and  unconsolidated,  and  the  two 
pairs  of  diaphanous  wings  were  alike  in  every  respect — in 
groups  that  have  since  developed  tegmina  and  dissimilar  tho- 
racic segments.  The  Carboniferous  precursors  of  our  cock- 
roaches, phasmids  and  May  flies  have  been  mentioned.  Palae- 
ozoic insects  are  grouped  by  Scudder  into  a  single  order, 
Palseodictyoptera,  on  account  of  their  synthetic  organization, 
though  other  authors  have  tried  to  distribute  them  among  the 
modern  orders.  This  disagreement  will  continue  until,  with 
increasing  knowledge,  our  classification  becomes  less  arbitrary 
and  more  natural. 

Mesozoic  insects  are  interesting  chiefly  as  evolutionary  links, 
notably  so  in  the  case  of  cockroaches — the  only  insects  whose 
ancestry  is  continuously  traceable.  In  this  era  the  large  fam- 
ilies became  differentiated  out. 

Most  of  the  Tertiary  species  are  referable  to  recent  genera, 
peculiar  families  being  highly  exceptional,  while  all  the  Quater- 
nary species  belong  to  recent  genera. 

Hemiptera  appear  in  the  Silurian;  Neuroptera  (in  the  old 
sense)  in  the  Devonian;  Thysanura  and  Orthoptera,  Carbonif- 
erous ;  Coleoptera  and  Hymenoptera,  Triassic ;  Diptera,  Juras- 
sic; and  Lepidoptera  not  until  the  Tertiary. 


CHAPTER    XITI 

INSECTS    IN    RELATION    TO    MAN 

A  great  many  insects,  eminently  successful  from  their  own 
standpoint,  so  to  speak,  nevertheless  interfere  seriously  with 
the  interests  of  man.  On  the  other  hand,  many  insects  are 
directly  or  indirectly  so  useful  to  man  that  their  services  form 
no  small  compensation  for  the  damage  done  hy  other  species. 

Injurious  Insects. — Insects  destroy  cultivated  plants,  infest 
domestic  animals,  injure  food,  manufactured  articles,  etc.,  and 
molest  or  harm  man  himself. 

The  cultivation  of  a  plant  in  great  quantity  offers  an  un- 
usual opportunity  for  the  increase  of  its  insect  inhahitants. 
The  numher  of  species  affecting-  one  kind  of  plant — to  say 
nothing  of  the  number  of  individuals — is  often  great.  Thus 
about  200  species  attack  Indian  corn,  50  of  them  doing  notable 
injury;  200  affect  clover,  directly  or  indirectly;  and  400  the 
apple ;  while  the  oaks  harbor  probably  i  .000  species. 

The  average  annual  loss  through  the  cotton  worm,  i860  to 
1874.  was  $15,000,000.  according  to  Packard;  the  loss  from 
the  Rocky  Mountain  locust,  in  1874,  in  Iowa,  Missouri.  Kan- 
sas and  Nebraska.  $40,000,000  (Thomas)  ;  and  the  total  loss 
from  this  pest,  1874  to  1877,  $200,000,000.  The  loss  through 
the  chinch  bug,  in  1864,  was  $73,000,000  in  Illinois  alone,  as 
estimated  by  Riley.  The  ravages  of  the  Hessian  fly,  fluted 
scale,  San  Jose  scale,  gypsy  moth  and  cotton  boll  weevil  need 
only  be  mentioned. 

At  times,  an  insect  has  been  the  source  of  a  national  calam- 
ity, as  was  the  case  for  forty  years  in  France,  when  Phylloxera 
threatened  to  exterminate  the  vine.  In  Africa  the  migratory 
locust  is  an  unmitigated  evil. 

Probably  at  least  ten  per  cent,  of  every  crop  is  lost  through 
the  attacks  of  insects,  though  the  loss  is  often  so  constant  as 

393 


394  ENTOMOLOGY 

to  escape  observation.  Regarded  as  a  direct  tax  of  ten  cents 
upon  the  dollar,  however,  this  loss  becomes  impressive.  Web- 
ster says :  "  It  costs  the  American  farmer  more  to  feed  his 
insect  foes  than  it  does  to  educate  his  children."  The  average 
annual  damage  done  by  insects  to  crops  in  the  United  States 
was  conservatively  estimated  by  Walsh  and  Riley  to  be  $300,- 
000,000 — or  about  $50  for  each  farm.  "  A  recent  estimate  by 
experts  put  the  yearly  loss  from  forest  insect  depredations  at 
not  less  than  $100,000,000.  The  common  schools  of  the  coun- 
try cost  in  1902  the  sum  of  $235,000,000,  and  all  higher  insti- 
tutions of  learning  cost  less  than  $50,000,000,  making  the  total 
cost  of  education  in  the  United  States  considerably  less  than 
the  farmers  lost  from  insect  ravages.  Thus  it  would  be  within 
the  statistical  truth  to  make  a  still  more  startling  statement 
than  Webster's,  and  say,  that  it  costs  American  farmers  more 
to  feed  their  insect  foes  than  it  does  to  maintain  the  whole 
system  of  education  for  everybody's  children. 

"  Furthermore,  the  yearly  losses  from  insect  ravages  aggre- 
gate nearly  twace  as  much  as  it  costs  to  maintain  our  army  and 
navy;  more  than  twice  the  loss  by  fire;  tw^ice  the  capital  in- 
vested in  manufacturing  agricultural  implements ;  and  nearly 
three  times  the  estimated  value  of  the  products  of  all  the  fruit 
orchards,  vineyards,  and  small  fruit  farms  in  the  country." 
(Slingerland.) 

Though  most  of  the  parasites  of  domestic  animals  are 
merely  annoyances,  some  inflict  serious  or  even  fatal  injury, 
as  has  been  said.  The  gad  flies  persecute  horses  and  cattle; 
the  maggots  of  a  hot  fly  grow  in  the  frontal  sinuses  of  sheep, 
causing  vertigo  and  often  death;  another  hot  fly  develops  in 
the  stomach  of  the  horse,  enfeebling  the  animal.  The  worst 
of  the  bot  flies,  however,  is  Hypoderma  lineata,  the  ox-warble, 
which  not  only  impairs  the  beef  but  damages  the  hide  by  its 
perforations ;  the  loss  from  this  insect  for  one  period  of  six 
months  (Chicago,  1889)  was  conservatively  estimated  as 
$3,336,565,  of  which  $667,513  represented  the  injury  to  hides. 

All  sorts  of  food  stuffs  are  attacked  by  insects,  particularly 


INSECTS  IN  RELATION  TO  MAN  395 

cereals ;  clothing-,  especially  of  wool,  fur  or  feathers ;  also  fur- 
niture and  hundreds  of  other  useful  articles. 

As  carriers  of  disease  germs,  insects  are  of  ^•ital  importance 
to  man,  as  we  have  shown. 

Beneficial  Insects. — The  vast  benefits  derived  from  insects 
are  too  often  o\-erlooked,  for  the  reason  that  they  are  often 
so  unobvious  as  compared  with  the  injuries  done  by  other  spe- 
cies. Insects  are  useful  as  checks  upon  noxious  insects  and 
plants,  as  pollenizers  of  tiowers.  as  scavengers,  as  sources  of 
human  clothing,  food,  etc.,  and  as  food  for  birds  and  fishes. 

Almost  every  insect  is  subject  to  the  attacks  of  other  insects, 
predaceous  or  parasitic — to  say  nothing  of  its  many  other 
enemies — and  but  for  this  a  single  species  of  insect  might  soon 
ox'errun  the  earth.  There  are  only  too  many  illustrations  of 
the  tremendous  spread  of  an  insect  in  the  absence  of  its  accus- 
tomed natural  enemies.  One  of  these  examples  is  that  of  the 
gypsy  moth,  artificially  introduced  into  Massachusetts  from 
Europe ;  another  is  the  fluted  scale,  transported  from  Australia 
to  California.  Some  conception  of  the  vast  restrictin^g  influ- 
ence of  one  species  upon  another  may  be  gained  from  the  fact 
that  the  fluted  scale  has  practically  been  exterminated  in  Cali- 
fornia as  the  result  of  the  importation  from  Australia  of  one 
of  its  natural  enemies,  a  lady-bird  beetle  known  as  Ahn'iiis  car- 
dinalis.  The  plant  lice,  though  of  unparalleled  fecundity,  are 
ordinarily  held  in  check  by  a  host  of  enemies,  as  w^as  described. 

An  astonishingly  large  number  of  parasites  may  develop  in 
the  body  of  a  single  individual ;  thus  over  3,000  specimens  of 
a  hymenopterous  parasite  {Copidosoina  truncatcUuin)  were 
reared  by  Giard  from  a  single  Pliisia  caterpillar. 

Parasites  themselves  are  frequently  parasitized,  this  phe- 
nomenon of  hyperparasitism  being  of  considerable  economic 
importance.  A  beneficial  primary  parasite  may  be  overpow- 
ered by  a  secondary  parasite,  evidently  to  the  indirect  disad- 
vantage of  man,  while  the  influence  of  a  tertiary  parasite  would 
be  beneficial  again.  Xow  parasites  of  the  third  order  occur 
and  probably  of  the  fourth  order,  as  appears  from  Howard's 


39^  ENTOMOLOGY 

studies,  which  we  have  already  summarized.  Moreover,  para- 
sites of  ah  degrees  are  attacked  by  predaceous  insects,  birds, 
bacteria,  fungi,  etc.  The  control  of  one  insect  by  another 
becomes,  then,  a  subject  of  extreme  intricacy. 

Insects  render  an  important,  though  commonly  unnoticed, 
service  to  man  in  checking  the  growth  of  weeds.  Indeed,  in- 
sects exercise  a  vast  influence  upon  vegetation  in  general.  A 
conspicuous  alteration  in  the  vegetation  has  followed  the  inva- 
sions of  the  Rocky  IMountain  locust,  as  Riley  has  said ;  many 
plants  before  unnoticed  have  grown  in  profusion  and  many 
common  kinds  have  attained  an  unusual  luxuriance. 

As  agents  in  the  cross  pollination  of  flowers,  insects  are 
eminently  important.  Darwin  and  his  followers  have  proved 
beyond  question  that  as  a  rule  cross  pollination  is  indispensable 
to  the  continued  vitality  of  flowering  plants ;  that  repeated 
close  pollination  impairs  their  vigor  to  the  point  of  extermina- 
tion. Without  the  visits  of  bees  and  other  insects  our  fruit 
trees  would  yield  little  or  nothing,  and  the  fruit  grower  owes 
these  helpers  a  debt  which  is  too  often  overlooked. 

As  scavengers,  insects  are  of  inestimable  benefit,  consuming 
as  they  do  in  incalculable  quantity  all  kinds  of  dead  and  decay- 
ing" animal  and  vegetable  matter.  This  function  of  insects  is 
most  noticeable  in  the  tropics,  where  the  ants,  in  particular, 
eradicate  tons  of  decomposing  matter  that  man  lazily  neglects. 

The  usefulness  of  the  silkworms  and  the  honey  bee  need 
only  be  mentioned,  and  after  these,  the  cochineal  insect  and  the 
lac  insects.  The  "  Spanish  fly  " — a  meloid  beetle — is  still  used 
medicinally,  and  in  China  medicinal  properties  are  ascribed 
to  many  different  insects.  As  human  food,  insects  are  of  con- 
siderable importance  among  semi-civilized  races ;  the  migra- 
tory locust  is  eaten  in  great  quantities  in  Africa,  and  termites 
in  Africa  and  Australia,  the  latter  insects  being  said  to  have 
a  delicious  flavor;  in  ]\Iexico  the  egg's  and  adults  of  an  aquatic 
hemipteron.  Corixa,  are  highly  relished  by  the  natives.  As 
food  for  fishes,  g-ame  birds,  song-  birds  and  poultry,  insects  are 
of  vast  importance,  it  is  needless  to  say. 


INSECTS    IN    RELATION    TO    MAN  397 

Introduction  and  Spread  of  Injurious  Insects. — Many  of 
(Uir  worst  insect  pests  were  Ijrought  accidentally  from  lun'ope. 
notably  the  Hessian  fly.  wheat  midg-e,  codling-  moth  (prob- 
ably), g'y])sy  moth,  cabbage  bntterlly.  cabbage  aphis,  clover 
leaf  beetle,  cloxer  root  borer,  asi)arag'ns  beetle,  imported  cur- 
rant worm  and  many  cutworms;  though  few  .American  species 
have  obtained  a  foothold  in  Europe,  one  of  the  few  being  the 
dreaded  Phylloxera,  which  appeared  in  France  in  1863. 

The  gypsy  moth,  liberated  in  Massachusetts  in  1868,  cost 
the  state  over  one  million  dollars  in  appropriations  (1890- 
1899)  and  is  not  yet  under  control.  The  San  Jose  scale,  a 
nati^■e  of  Xorth  China  according  to  ]\Iarlatt,  was  introduced 
into  the  San  Jose  valley,  California,  about  1870,  proljably  upon 
the  flowering  Chinese  peach,  became  seriously  destructive  there 
in  1873.  "^'^'''-s  carried  across  the  continent  to  New  Jersey  in 
1886  or  1887  on  plum  stock,  and  thence  distributed  directly  to 
several  other  states,  upon  nursery  stock.  At  present  the  San 
Jose  scale  is  a  permanent  menace  to  horticulture  throughout 
the  United  States  and  is  being  checked  or  subdued  only  by  the 
vigorous  and  continuous  work  of  official  entomologists,  acting 
under  special  legislation.  This  pernicious  insect  occurs  also 
in  Japan,  Hawaii,  Australia  and  Chile,  in  these  places  probably 
as  a  recent  introduction. 

The  Mexican  cotton  boll  weevil  (Aiitlioiioinus  graiidis) 
crossed  the  Rio  Grande  river  and  appeared  in  Brownsville, 
Texas,  about  1892,  since  when  it  has  spread  over  eastern  Texas 
and  even  into  western  Louisiana.  Advancing  as  it  does  at 
the  rate  of  fifty  miles  a  year,  the  insect  would  require  but  fif- 
teen or  eighteen  years  to  cover  the  entire  cotton  belt.  The 
beetle  hibernates  and  lays  its  eg'gs  in  the  cotton  bolls ;  these 
are  injured  both  by  the  larva  feeding  within  and  by  the  beetles, 
whose  feeding-punctures  destroy  the  bolls  and  cause  them  to 
drop.  If  unchecked,  this  pest  would  destroy  fully  one  half  the 
cotton  crop,  entailing  an  annual  loss  of  $250,000,000.  As  it 
is,  the  universal  adoption  of  the  cultural  methods  recommended 
by  the  Bureau  of  Entomology  promises  to  reduce  the  damage 
to  a  point  at  which  cotton  can  still  be  grown  at  a  fair  profit. 


398  ENTOMOLOGY 

An  insect  often  passes  readily  from  a  wild  plant  to  a  nearly 
related  cultivated  species.  Thus  the  Colorado  potato  beetle 
passed  from  the  wild  species  Solaiiuni  rostratuin  to  the  intro- 
duced species,  Solannni  tuhcrosnm,  the  potato.  Many  of  our 
fruit  tree  insects  feed  upon  wild,  as  well  as  cultivated,  species 
of  Rosace?e  ;  the  peach  borer,  a  native  of  this  country,  probably 
fed  orig-inally  upon  wild  plum  or  wild  cherry.  Many  of  the 
common  scarab.neid  larvae  known  as  "  white  grubs  "  are  native 
to  prairie  sod,  and  attack  the  roots  of  various  cultivated  grasses, 
including  corn,  and  those  of  strawberry,  potato  and  other 
plants.  The  chinch  bug  fed  originally  upon  native  grasses, 
but  is  ecjually  at  home  on  cultivated  species,  particularly  millet, 
Hungarian  grass,  rice,  wheat,  barley,  rye  and  corn.  In  fact, 
the  worst  corn  insects,  such  as  the  chinch  bug,  wire  w^orms. 
white  grubs  and  cutworms,  are  species  derived  from  wild 
grasses. 

Even  in  the  absence  of  cultivated  plants  their  insect  pests 
continue  to  sustain  themselves  upon  wild  plants,  as  a  rule ;  the 
larva  of  the  codling  moth  is  very  common  in  wild  apples  and 
wild  haws. 

The  Economic  Entomologist. — To  mitigate  the  tremen- 
dous damage  done  by  insects,  the  individual  cultivator  is  almost 
helpless  without  expert  advice,  and  the  immense  agricultural 
interests  of  this  country  have  necessitated  the  development  of 
the  economic  entomologist,  the  value  of  whose  services  is  uni- 
versally appreciated  by  the  intelligent. 

Nearly  every  State  now  has  one  or  more  economic  entomolo- 
gists, responsible  to  the  State  or  else  to  a  State  Experiment 
Station,  while  the  general  Government  attends  to  general  ento- 
mological needs  in  the  most  comprehensive  and  thorough 
manner. 

"  It  is  the  special  object  of  the  economic  entomologist," 
says  Dr.  Forbes,  "  to  investigate  the  conditions  under  which 
these  enormous  losses  of  the  food  and  labor  of  the  country 
occur,  and  to  determine,  first,  whether  any  of  them  are  in  any 
degree  preventable;  second,  if  so,  how  they  are  to  be  prevented 


INSECTS  IN  RELATION  TO  MAN  399 

with  the  least  possil)le  cost  of  lalxM"  and  monev;  and.  tliird,  to 
estimate  as  exactly  as  possihle  the  expenses  of  such  prevention, 
or  to  furnish  the  data  for  such  an  estimate,  in  order  that  each 
may  determine  for  himself  what  is  for  his  interest  in  every 
case  arising-. 

"  The  suhject  matter  of  this  science  is  not  insects  alone,  nor 
plants  alone,  nor  farmini^-  alone.  One  may  he  a  most  excellent 
entomologist  or  hotanist.  or  he  may  ha\c  the  whole  theory  and 
practice  of  agriculture  at  his  tongue's  end,  and  at  his  fingers'' 
ends  as  Avell,  and  yet  he  without  knowdedge  or  resources  when, 
brought  face  to  face  with  a  new  practical  prol)lem  in  economic 
entomology.  The  suhject  is  essentially  that  of  the  relations 
of  these  things  to  each  other ;  of  insect  to  plant  and  of  plant 
to  insect,  and  of  both  these  to  the  purposes  and  operations  of 
the  farm,  and  it  involves  some  knowdedge  of  all  of  them. 

"  As  far  as  the  entomological  part  of  the  subject  is  con- 
cerned, the  chief  requisites  are  a  familiar  acquaintance  with 
the  common  injurious  insects,  and  especially  a  thorough 
knowledge  of  their  life  histories,  together  wdth  a  practical 
familiarity  with  methods  of  entomological  study  and  research. 
The  life  histories  of  insects  lie  at  the  foundation  of  the  whole 
subject  of  economic  entomology ;  and  constitute,  in  fact,  the 
principal  part  of  the  science;  for  until  these  are  clearly  and 
completely  made  out  for  any  given  injurious  species,  we  can- 
not possibly  tell  when,  where  or  how  to  strike  it  at  its  weakest 
point. 

"  But  besides  this,  we  must  also  know  the  conditions  favor- 
able and  unfavorable  to  it ;  the  enemies  wdiich  prey  upon  it, 
whether  bird  or  insect  or  plant  parasite ;  the  diseases  to  which 
it  is  subject,  and  the  effects  of  the  various  changes  of  weather 
and  season.  W^e  should  make,  in  fact,  a  thorough  study  of 
it  in  relation  to  the  whole  system  of  things  by  wdiich  it  is 
affected.  Without  this  we  shall  often  be  exposed  to  needless 
alarm  and  expense,  perhaps,  in  fighting  by  artificial  remedies, 
an  insect  already  in  process  of  rapid  extinction  by  natural 
causes ;  perhaps  giving  up  in  despair  just  at  the  time  when  the 


400  ENTOMOLOGY 

natural  checks  upon  its  career  are  about  to  lend  their  powerful 
aid  to  its  suppression.  We  may  even,  for  lack  of  this  knowl- 
edge, destroy  our  best  friends  under  the  supposition  that  they 
are  the  authors  of  the  mischief  which  they  are  really  exerting 
themselves  to  prevent.  In  addition  to  this  knowledge  of  the 
relations  of  our  farm  pests  to  what  we  may  call  the  natural 
conditions  of  their  life,  we  must  know  how  our  own  artificial 
farming  operations  affect  them,  which  of  our  methods  of  cul- 
ture stimulate  their  increase,  and  which,  if  any,  may  help  to 
keep  it  down.  And  we  must  also  learn  where  strictly  artifi- 
cial measures  can  be  used  to  advantage  to  destroy  them. 

"  For  the  life  histories  of  insects,  close,  accurate  and  con- 
tinuous observation  is  of  course  necessary ;  and  each  species 
studied  must  be  followed  not  only  through  its  periods  of  de- 
structive abundance,  w^hen  it  attracts  general  attention,  but 
through  its  times  of  scarcity  as  well,  and  season  after  season, 
and  year  after  year. 

''  The  observations  thus  made  must  of  course  be  collected, 
collated  and  most  cautiously  generalized,  wdth  constant  refer- 
ence to  the  conditions  under  which  they  were  made.  No  part 
of  the  work  requires  more  care  than  this. 

"  This  work  becomes  still  more  ditificult  and  intricate  when 
we  pass  from  the  simple  life  histories  of  insects  to  a  study  of 
the  natural  checks  upon  their  increase.  Here  hundreds  and 
even  thousands  of  dissections  of  insectivorous  birds  and  pre- 
daceous  insects  are  necessary,  and  a  careful  microscopic  study 
of  their  food,  followed  by  summaries  and  tables  of  the  prin- 
cipal results,  a  tedious  and  laborious  undertaking,  a  specialty 
in  itself,  recjuiring  its  special  methods  and  its  special  knowl- 
edge of  the  structures  of  insects  and  plants,  since  these  must 
be  recognized  in  fragments,  while  the  ordinary  student  sees 
them  only  entire. 

"  If  we  would  understand  the  relations  of  season  and 
weather  to  the  abundance  of  injurious  insects,  we  are  led  up 
to  the  science  of  meteorology;  and  if  w^e  undertake  to  master 
the  obscure  subject  of  their  diseases,  especially  those  of  epi- 


INSECTS  IN  RELATION  TO  MAN  4O I 

demic  or  contag'ious  character,  we  sliall  find  use  for  the  highest 
skill  of  the  microscopist.  and  the  best  instruments  of  micro- 
scopic research. 

"  All  these  investigations  are  preliminary  to  the  practical 
part  of  our  subject.  What  shall  the  farmer  do  to  protect  his 
crops?  To  answer  this  question,  besides  the  studies  just  men- 
tioned, much  careful  experiment  is  necessary.  All  practical 
methods  of  fighting  the  injurious  insects  must  be  tried — first 
on  a  small  scale,  and  under  conditions  which  the  experimenter 
can  control  completely,  and  then  on  the  larger  scale  of  actual 
practice ;  and  these  experiments  must  be  repeated  under  vary- 
ing circumstances,  until  we  are  sure  that  all  chances  of  mistake 
or  of  accidental  coincidence  are  removed.  The  whole  subject 
of  artificial  remedies  for  insect  depredations,  whether  topical 
applications  or  special  modes  of  culture,  must  be  gone  over 
critically  in  this  way.  So  many  of  the  so-called  experiments 
upon  which  current  statements  relating  to  the  value  of  reme- 
dies and  preventives  are  based,  have  been  made  by  persons 
unused  to  investigation,  ignorant  of  the  habits  and  the  trans- 
formations of  the  insects  treated,  without  skill  or  training  in 
the  estimation  of  evidence,  and  failing  to  understand  the  im- 
portance of  verification,  that  the  whole  subject  is  honeycombed 
with  blunders.  Popular  remedies  for  insect  injuries  have,  in 
fact,  scarcely  more  value,  as  a  rule,  than  popular  remedies  for 
disease. 

"  Observation,  record,  generalization,  experiment,  verifica- 
tion— these  are  the  processes  necessary  for  the  mastery  of  this 
subject,  and  they  are  the  principal  and  ordinary  processes  of 
all  scientific  research." 

The  official  economic  entomologist  uses  every  means  to 
reach  the  public  for  whose  benefit  he  works.  Bulletins,  circu- 
lars and  reports,  embodying  most  serviceable  information,  are 
distributed  freely  where  they  will  do  the  most  good,  and  timely 
advice  is  disseminated  through  newspapers  and  agricultural 
journals.  An  immense  amount  of  correspondence  is  carried 
on  with  individual  seekers  for  help,  and  personal  influence  is 
27 


402  ENTOMOLOGY 

exerted  in  visits  to  infested  localities  and  by  addresses  before 
agricultural  meetings.  Special  emergencies  often  tax  every 
resource  of  the  official  entomologist,  especially  if  he  is  ham- 
pered by  inadequate  legislative  provision  for  his  work.  Too 
often  the  public,  disregarding  the  prophetic  voice  of  the  expert, 
refuses  to  "  close  the  door  until  the  horse  is  stolen." 

Aside  from  these  emergencies,  such  as  outbreaks  of  the 
Rocky  Mountain  locust,  chinch  bug,  Hessian  fly,  San  Jose 
scale  and  others,  the  State  or  Experiment  Station  entomologist 
has  his  hands  full  in  any  State  of  agricultural  importance ;  in 
fact,  can  scarcely  discharge  his  duties  properly  without  the  aid 
of  a  corps  of  competent  assistants. 

This  chapter  would  be  incomplete  without  some  mention  of 
the  progress  of  economic  entomology  in  this  country,  especially 
since  America  is  pre-eminently  the  home  of  the  science.  The 
history  of  the  science  is  largely  the  history  of  the  State  and 
Government  entomologists,  for  the  following  account  of  whose 
work  we  are  indebted  chiefly  to  the  writings  of  Dr.  Howard, 
to  which  the  reader  is  referred  for  additional  details  as  well 
as  for  a  comprehensive  review  of  the  status  of  economic  ento- 
mology in  foreig'n  countries. 

Massachusetts. — Dr.  Thaddeus  W.  Harris,  though  preceded 
as  a  writer  upon  economic  entomology  by  William  D.  Peck, 
was  our  pioneer  official  entomologist — official  simply  in  the 
sense  that  his  classic  volume  was  prepared  and  published  at 
the  expense  of  the  state  of  Massachusetts,  first  (1841)  as  a 
"  Report  "  and  later  as  a  "  Treatise."  The  splendid  Flint 
edition  (1862),  entitled  "A  Treatise  on  Some  of  the  Insects 
Injurious  to  Vegetation,"  is  still  "  the  z'cuic  mccum  of  the 
working  entomologist  who  resides  in  the  northeastern  section 
of  the  country." 

Dr.  Alpheus  S.  Packard  gave  the  state  three  short  but  use- 
ful reports  from  1871  to  1873. 

As  entomologist  to  the  Hatch  Experiment  Station  of  the 
Massachusetts  Agricultural  College,  Prof.  Charles  H.  Fernald 
has  issued  important  bulletins  upon  injurious  insects,  and  has 


INSECTS    IN    RELATION    TO    MAN  4O3 

publisliecl  ill  collalxn-atioii  willi  Edward  II.  Forbush  a  notable 
volume  upon  the  i;ypsy  moth.  For  the  suppression  of  this 
pest,  which  threatened  to  exterminate  ve.^-etation  over  one  hun- 
dred square  miles,  the  state  of  Massachusetts  made  annual 
appropriations  amounting"  in  all  to  more  than  one  million  dol- 
lars, and  the  operations,  carried  on  by  a  committee  of  the  State 
Board  of  Agriculture,  rank  among  the  most  extensive  of  their" 
kind. 

New  York. — Dr.  .\sa  Fitch,  appointed  in  1854  by  the  New 
York  State  Agricultural  Society,  under  the  authorization  of 
the  legislature,  was  the  first  entomologist  to  be  officially  com- 
missioned by  any  state.  His  fourteen  repcjrts  (1855  to  1872) 
embody  the  results  of  a  large  amount  of  painstaking  investi- 
gation. 

In  1881,  Dr.  James  A.  Lintner  became  state  entomologist 
of  New  York.  Highly  competent  for  his  chosen  work,  Lint- 
ner made  every  effort  to  further  the  cause  of  economic  ento- 
mology, and  his  thirteen  reports,  accurate,  thorough  and  ex- 
tremely serviceable,  rank  among  the  best. 

Lintner  has  had  a  most  able  successor  in  Dr.  E.  P.  Felt,  who 
is  continuing  the  work  with  exceptional  vigor  and  the  most 
careful  regard  for  the  entomological  welfare  of  the  state. 
Felt  has  published  at  this  writing  eighteen  bulletins  (including 
seven  annual  reports),  besides  important  papers  on  forest  and 
shade  tree  insects,  and  has  directed  the  preparation  by  Need- 
ham  and  his  associates  of  three  notable  volumes  on  aquatic 
insects. 

The  Cornell  Laiiversity  Agricultural  Experiment  Station, 
established  in  1879,  ^^^^  issued  many  valual)le  publications 
upon  injurious  insects,  written  by  the  master-hand  of  Pro- 
fessor Comstock  or  else  under  his  influence.  The  studies  of 
Comstock  and  Slingerland  are  always  made  in  the  most  con- 
scientious spirit  and  their  bulletins — original,  thorough  and 
practical — are  models  of  what  such  works  should  be. 

Illinois. — Mr.  Benjamin  D.  Walsh,  engaged  in  1867  by  the 
Illinois  State  Horticultural  Society,  published  in  1868,  as  act- 


404  ENTOMOLOGY 

ing  state  entomologist,  a  report  in  the  interests  of  horticulture 
— an  accurate,  sagacious  and  altogether  excellent  piece  of  ori- 
ginal work.  Like  many  other  economic  entomologists  he  was 
a  prolific  writer  for  the  agricultural  press  and  his  contribu- 
tions, numbering  about  four  hundred,  were  in  the  highest 
degree  scientific  and  practical. 

Walsh  was  succeeded  by  Dr.  William  LeBaron,  who  pub- 
lished (1871  to  1874)  four  able  reports  of  great  practical 
value.  In  the  words  of  Dr.  Howard,  "  He  records  in  his  first 
report  the  first  successful  experiment  in  the  transportation  of 
parasites  of  an  injurious  species  from  one  locality  to  another, 
and  in  his  second  report  recommended  the  use  of  Paris  green 
against  the  canker  worm  on  apple  trees,  the  legitimate  outcome 
from  which  has  been  the  extensive  use  of  the  same  substance 
against  the  codling  moth,  which  may  safely  be  called  one  of 
the  great  discoveries  in  economic  entomology  of  late  years." 

Following  LeBaron  as  state  entomologist,  Rev.  Cyrus 
Thomas  and  his  assistants,  G.  H.  French  and  D.  W.  Coquillett, 
produced  a  creditable  series  of  six  reports  (1875  to  1880)  as 
part  of  a  projected  manual  of  the  economic  entomology  of 
Illinois. 

Since  1882,  Prof.  Stephen  A.  Forbes  has  fulfilled  the  duties 
of  state  entomologist  in  the  most  efficient  manner.  Thor- 
oughly scientific,  with  a  broad  view  and  a  clear  insight  into 
the  agricultural  needs  of  the  state,  his  authoritative  and  schol- 
arly works  upon  economic  entomology  rank  with  those  of  the 
highest  value.  Of  the  twelve  reports  issued  thus  far  by  Dr. 
Forbes,  those  dealing  with  the  chinch  bug,  San  Jose  scale,  corn 
insects  and  sugar  beet  insects  are  especially  noteworthy. 

Missouri. — Appointed  in  1868,  Prof.  Charles  V.  Riley  pub- 
lished (1869  to  1877)  nine  reports  as  state  entomologist.  To 
quote  Dr.  Howard,  "  They  are  monuments  to  the  state  of  Mis- 
souri, and  more  especially  to  the  man  who  wrote  them.  They 
are  original,  practical  and  scientific.  .  .  .  They  may  be  said  to 
have  formed  the  basis  for  the  new  economic  entomology  of 
the  world."  Riley's  subsequent  work  will  presently  be  spoken 
of. 


INSECTS  IN  RELATION  TO  MAN  4O5 

State  Experiment  Stations. — The  oro-anization  of  State 
Agricultural  Experiment  Stations  in  1888,  under  the  Hatch 
Act,  gave  economic  entomology  an  additional  impetus.  At 
present,  all  the  states  and  territories,  except  Indian  Territory, 
have  an  experiment  station,  and  in  a  few  instances  two  or  even 
three;  while  there  are  stations  in  Alaska,  Hawaii  and  Porto 
Rico.  These  stations,  often  in  connection  with  state  agricul- 
tural colleges,  maintain  altogether  over  forty  men  who  con- 
cern themselves  more  or  less  with  entomology,  and  have  issued 
a  great  numher  of  bulletins  upon  injurious  insects.  These 
publications  are  extremely  valuable  as  a  means  of  disseminat- 
ing entomological  information,  and  not  a  few  of  them  are 
based  upon  the  investigations  of  their  authors.  Especially 
noteworthy  as  regards  originality,  volume  and  general  useful- 
ness are  the  publications  of  Slingerland  in  New  York.  Smith 
in  New  Jersey,  Webster  in  Ohio  (formerly),  Hopkins  in  West 
Virginia,  Gillette  and  Osborn  in  Iowa  and  Gillette  in  Colorado. 
The  reports  that  Lugger  issued  in  Minnesota,  though  compiled 
for  the  most  part,  contain  much  serviceable  information,  pre- 
sented in  a  popularly  attractive  manner. 

While  these  workers  have  been  conspicuously  active  in  the 
publication  of  their  investigations,  there  are  many  other  sta- 
tion entomologists  who  devote  themselves  altogether  to  the 
practical  application  of  entomological  knowledge,  and  whose 
work  in  this  respect  is  highly  important,  even  though  its  influ- 
ence does  not  extend  beyond  the  limits  of  the  state. 

The  U.  S.  Entomological  Commission. — This  commission 
founded  under  a  special  Act  of  Congress  in  1877  to  investigate 
the  Rocky  JNIountain  locust,  consisted  of  Dr.  C.  V.  Riley,  Dr. 
A.  S.  Packard  and  Rev.  Cyrus  Thomas,  remained  in  existence 
until  1 88 1,  and  published  five  reports  and  seven  bulletins,  all 
of  lasting  value.  The  first  two  reports  form  a  most  elaborate 
monograph  of  the  Rocky  Mountain  locust;  the  third  report 
includes  important  work  upon  the  army  worm  and  the  canker 
worm ;  the  fourth,  written  by  Riley,  is  an  admirable  volume  on 
the  cotton  w^orm  and  boll  worm ;  and  the  fifth,  by  Packard,  is 
a  useful  treatise  on  forest  and  shade  tree  insects. 


406  ENTOMOLOGY 

The  U.  S.  Department  of  Agriculture. — The  first  ento- 
mological expert  appointed  under  the  general  government  was 
Townend  Glover,  in  1854.  He  issued  a  large  number  of 
reports  (1863-1877),  which  "are  storehouses  of  interesting 
and  important  facts  which  are  too  little  used  by  the  working 
entomologists  of  to-day,"  as  Howard  says.  Glover  prepared, 
moreo\'er,  a  most  elaborate  series  of  illustrations  of  North 
American  insects,  at  an  enormous  expense  of  labor,  out  of  all 
proportion,  however,  to  the  practical  value  of  his  undertaking. 

Glover  was  succeeded  in  1878  by  Riley,  whose  achievements 
have  aroused  international  admiration.  He  resigned  in  a  year, 
after  writing  a  report,  and  was  succeeded  by  Prof.  Comstock, 
who  held  office  for  two  years,  during  which  he  wrote  two 
important  volumes  (published  respectively  in  1880  and  1881) 
dealing  especially  with  cotton,  orange  and  scale  insects.  His 
work  on  scale  insects  laid  the  foundation  for  all  our  subsequent 
investigation  of  the  subject. 

Riley,  assuming  the  ofiice  of  government  entomologist,  pub- 
lished up  to  1894,  "12  annual  reports,  31  bulletins,  2  special 
reports,  6  volumes  of  the  periodical  bulletin  Insect  Life,  and 
a  large  number  of  circulars  of  information."  During  his 
vigorous  and  enterprising  administration  economic  entomology 
took  an  immense  step  in  advance.  The  life  histories  of  injuri- 
ous insects  were  studied  with  extreme  care  and  many  valuable 
improvements  in  insecticides  and  insecticide  machinery  were 
made.  One  of  the  notable  successes  of  Dr.  Riley  and  his  co- 
workers, which  has  attracted  an  exceptional  amount  of  public 
attention,  was  the  practical  extermination  of  the  fluted  scale 
(Iccrya  piirchasi),  which  threatened  to  put  an  end  to  the  cul- 
tivation of  citrus  trees  in  California.  This  disaster  was 
averted  by  the  importation  from  Australia,  in  1888,  of  a  native 
enemy  of  the  scale,  namely,  the  lady-bird  beetle  Ahviits 
(Fcdalia)  cardiiialis,  which,  in  less  than  eighteen  months  after 
its  introduction  into  California,  subjugated  the  noxious  scale 
insect.  The  United  States  has  since  sent  Noz'ius  to  South 
Africa,  Egypt  and  Portugal  with  similar  beneficial  results. 


INSECTS  IN  RELATION  TO  MAN  AOJ 

Based  upon  the  foundation  laid  Ijy  Riley,  the  work  of  the 
Division  (now  the  Bureau)  of  Entomology  has  steadily  pro- 
gressed, under  the  leadership  of  Dr.  Leland  O.  Howard.  With 
a  comprehensixe  and  linn  grasp  of  his  snhject,  alert  to  discover 
and  develoj)  new  possibilities,  energetic  and  resourceful  in 
management.  Dr.  Howard  has  brought  the  go\-ernment  work 
in  applied  entomology  to  its  present  position  of  commanding 
importance.  Admirably  organized,  the  Bureau  now  maintains 
a  corps  of  about  fifty  experts,  and  the  total  output  of  the  Divi- 
sion and  the  Bureau  now  amounts  to  nearly  one  hundred  bul- 
letins and  more  than  half  as  many  circulars. 

The  Department  of  Agriculture  has  recently  succeeded  in 
starting  a  new  and  important  industry  in  California — the  cul- 
ture of  the  Smyrna  fig.  The  superior  flavor  of  this  variety 
is  due  to  the  presence  of  ripe  seeds,  or,  in  other  words,  to 
fertilization,  and  for  this  it  is  necessary  for  pollen  of  the  wdld 
fig,  ox  "  caprifig,"  to  be  transferred  to  the  flowers  of  the 
Smyrna  fig.  Normally  this  pollination,  or  "  caprification," 
is  dependent  upon  the  services  of  a  minute  chalcid,  BlastopJi- 
aga  grossoniiit,  which  develops  in  the  gall-like  flow'ers  of 
the  caprifig.  The  female  insect,  wdiich  in  this  exceptional  in- 
stance is  winged  while  the  male  is  not,  emerges  from  the  gall 
co\'ered  with  pollen,  enters  the  young  flowers  of  the  Smyrna 
fig  to  oviposit,  and  incidentally  pollenizes  them. 

After  many  discouraging-  attempts.  Blastophaga,  imported 
from  Algeria,  has  now  been  established  in  California,  and  the 
new  industry  is  developing  rapidly. 

Canada. — The  development  of  economic  entomology  in 
Canada  has  been  due  largely  to  the  eft'orts  of  Dr.  James 
Fletcher,  of  the  Dominion  Experimental  Earms,  Ottawa, 
whose  annual  reports  and  other  writings  indicate  ability  of  an 
exceptional  order.  His  work  has  been  furthered  in  every  way 
by  the  "  eminent  director  of  the  experimental  farms  system. 
Dr.  William  Saunders,  himself  a  pioneer  in  economic  ento- 
mology in  Canada  and  the  author  of  one  of  the  most  valuable 
treatises  upon  the  subject  that  has  ever  been  published  in 
America." 


408  ENTOMOLOGY 

Outside  of  this,  the  work  in  Canada  centers  around  the 
Entomological  Society  of  Ontario,  whose  excellent  publica- 
tions, sustained  by  the  government,  are  of  great  scientific  and 
educational  importance.  In  addition  to  its  annual  reports,  this 
society  issues  the  Canadian  Entomologist,  one  of  the  leading 
serials  of  its  kind,  edited  by  its  founder,  the  Rev.  C.  J.  S. 
Bethune,  whose  devoted  services  are  appreciated  by  every 
entomologist. 

The  Association  of  Official  Economic  Entomologists. — 
Organized  in  1889  by  a  few  energetic  workers,  this  association 
has  had  a  rapid  and  healthy  growth  and  now  numbers  among 
its  members  all  the  leading  economic  entomologists  of  America 
and  a  large  number  of  foreign  workers.  The  annual  meetings 
of  the  association  impart  a  vigorous  stimulus  to  the  individual 
worker  and  tend  to  promote  a  well-balanced  development  of 
the  science  of  economic  entomology. 

Conclusion. — While  working  for  the  material  welfare  of 
the  agriculturist,  the  economic  entomologist  discovers  phe- 
nomena which  are  of  the  highest  value  to  the  purely  scientific 
mind.  Indeed  it  is  remarkable  to  notice  the  extent  to  which 
the  professedly  practical  entomologist  is  animated — not  to  say 
dominated — by  the  same  spirit  which  has  led  many  of  the  most 
profound  thinkers  that  the  world  has  ever  produced  to  devote 
their  lives  to  the  study  of  life  itself. 


LITERATURE 

The  literature  on  entomological  subjects  now  numbers  scarcely  less  than 
100.000  titles.  The  works  listed  below  have  been  selected  chiefly  on 
account  of  their  general  usefulness  and  accessibility.  Works  incidentally 
containing  important  bibliographies  of  their  special  subjects  are  designated 
each  by  an  asterisk — *. 

BIBLIOGRAPHICAL   WORKS 

Hagen,    H.    A.      Bibliotheca    Entomologica.      2    vols.      Leipzig,    1862-1863. 

Covers  the  entire  literature  of  entomology  up  to  1862. 
Engelmann,   W.      Bibliotheca   Historico-Naturalis.      i   vol.      Leipzig,    1846. 

Literature,   1700-1846. 
Carus,  J.  v.,  and  Engelmann,  W.     Bibliotheca  Zoologica.     2  vols.     Leipzig, 

1861.     Literature,  1846-1860. 
Taschenberg,     0.      Bibliotheca     Zoologica.      5     vols.      Leipzig,     1887-1899. 

Vols.  2  and  3,  entomological  literature,   1861-1880. 
The  Zoological  Record.     London.     Annually  since  vol.  for  1864. 
Catalogue  of  Scientific  Papers,  Royal  Society.     London.     Since   1868. 
Zoologischer    Anzeiger.     Leipzig.     Fortnightly    since    1878.     Bibliographica 

Zoologica,   annual  volumes   since   1896. 
Concilium  Bibliographicum.     Zurich.     Card  catalogue  of  current  zoological 

literature  since   1896. 
Archiv  fiir  Naturgeschichte.     Berlin.     Annual  summaries  since  1835. 
Journal  of  the  Royal  Microscopical  Society.     London.     Summaries  of  the 

most  important  works,  beginning  1878. 
Zoologischer    Jahresbericht.      Leipzig.      Yearly     summaries     of     literature 

since  1879. 
Zoologisches    Centralblatt.     Leipzig.     Reviews    of    more    important    litera- 
ture since   1895. 
Psyche.     Cambridge,  Mass.     Records  of  recent  American  literature.     Also 

earlier  records,  beginning  1874. 
Entomological  News.     Philadelphia,  1890  to  date.     Records  of  current  lit- 
erature up  to  1903. 
Bibliography  of  the  more  important  contributions  to  American  Economic 

Entomology.     8  parts.     Pts.   1-5  by  S.  Henshaw ;  pts.  6-S  by  N. 

Banks.     1318    pp.     Washington,     18S9-1905. 
Catalogue   of   Scientific    Serials,    1633-1876.     S.    H.    Scudder.     Cambridge, 

Mass.     Harvard   University,   1879. 
A   Catalogue    of    Scientific    and    Technical   Periodicals,    1665-1895.     H.    C. 

Bolton.     Washington,   Smithsonian  Institution,   1897. 

409 


41 0  ENTOMOLOGY 

A  List  of  Works  on  North  American  Entomology.     N.  Banks.     Bull.  U.  S. 
Dept.  Agric,  Div.  Ent.,  no.  24   (n.  s.j,  95  pp.     Washington,   1900. 

GENERAL    ENTOMOLOGY 

Kirby,   W.,    and    Spence,   W.     1822-26.     An    Introduction   to    Entomology. 

4  vols.     36  +  2413  pp.,  30  pis.     London. 
Burmeister,  H.     1832-55.     Handbuch  der  Entomologie.     2  vols.     28 -|- 1746 

pp.,   16  taf.     Trans,  of  Band  i  :  1836.     W.  E-  Shuckard.     A  Man- 
ual of  Entomology.     12  +  654  pp..  32  pis.     London. 
Westwood,  J.  0.     1839-40.     An  Introduction  to  the   Modern  Classification 

of  Insects.     2  vols.     23  +  620  pp.,   133  figs.     London. 
Graber,    V.      1877-79.      Die    Insekten.      2    vols.      8+1008    pp.,    404    figs. 

]\Iimchen. 
Miall,  L.  C,  and  Denny,  A.     1886.     The  Structure  and  Life-History  of  the 

Cockroach.     6  +  224  pp.,  125  figs.     London,  Lovell  Reeve  &  Co. ; 

Leeds,  R.  Jackson. 
Comstock,  J.  H.     1888.     An  Introduction  to  Entomology.     4  +  234  pp.,  201 

figs.     Ithaca,  N.  Y. 
Kolbe,  H.  J.     1889-93.     Einfiihrung  in   die   Kenntnis   der   Insekten.     12  + 

709   pp.,    324   figs.     Berlin.     F.    Diimmler.* 
Packard,  A.  S.     1889.     Guide  to  the  Study  of  Insects.     Ed.   9,     12  +  715 

pp.,  668  figs.,  IS  pis.     New  York.     Henry  Holt  &  Co. 
Hyatt,  A.,  and  Arms,  J.  M.     1890.     Insecta.     23  +  300  pp..  13  pis.,  223  figs. 

Boston.     D.  C.   Heath  &  Co.* 
ICirby,  W.  F.     1892.     Elementary  Text-Book  of  Entomology.     Ed.  2.     8  + 

281  pp.,  87  pis.     London.     Swan  Sonnenschein  &  Co. 
Comstock,  J.  H.  and  A.  B.      1895.      A   Manual   for  the   Study  of   Insects. 

7  +  701  pp.,  797  figs.,  6  pis.     Ithaca,  N.  Y.     Comstock  Pub.  Co. 
Sharp,  D.     1895,  1901.     Insects.     Cambr.  Nat.  Hist.,  vols.  5,  6.     12+ 1 130 

pp.,  618  figs.     London  and  New  York.     Macmillan  &  Co.* 
Comstock,  J.  H.     1897,   1901.     Insect  Life.     6  +  349  PP--   18  pis.,   296  figs. 

New  York.     D.  Appleton  &  Co. 
Packard,  A.  S.      1898.      A  Text-Book  of  Entomology.      17  +  729  pp.,  654 

figs.     New  York  and  London.     The  Macmillan  Co.* 
Carpenter,  G.  H.     1899.     Insects;  their  Structure  and  Life.     11  +  404  pp., 

184  figs.     London.     J.   M.   Dent  &  Co.* 
Packard,  A.  S.     1899.     Entomology  for  Beginners.     Ed.  3.     16  +  367  pp., 

273  figs.     New  York.     Henry  Holt  &  Co.* 
Howard,   L.  0.     1901.     The   Insect   Book.     27  +  429  pp.,  48  pis.,  264   figs. 

New  York.     Doubleday,  Page  &  Co. 
Hunter,    S.   J.     1902.     Elementary    Studies    in    Insect    Life.     18  +  344   PP- 

234  figs.     Topeka.     Crane  &  Co. 
Henneguy,   L.    F.     1904.     Les    Insectes.     INIorphologie,    Reproduction,    Em- 

bryogenie.     18  +  804  pp.,  622  figs.,  4  pis.     Paris.     Masson  et  Cie.* 
Kellogg    V.    L.     1905.     American    Insects.     7  +  674    pp.,    13    pis.,    812    figs. 

New  York.     Henry  Holt  &  Co. 


LITERATURE  4I  I 


PIIYLOGENY   AND    CLASSIFICATION 

Kirby,   W.,   and   Spence,    W.     1822-26.     An    Introduction    to    ICntomology. 

4  vols.     36  4" -413  PP"  30  pis.     London. 
Burmeister,  H.      1832.      Handbuch   der  Entomologie.      2  vols.      284-1746 

pp.,  16  laf.     Berlin.     Translation  of  Band  i  :  1836.     W.  E.  Shuck- 

ard.     A   .Manual   of   Entomology.     12  +  654  PP-.   32  pis.     London. 

Contains   useful   synopses  of  the  older  systems  of  classification. 
Westwood,  J.  0.     1839-40.     An  Introduction  to  the  Modern  Classification 

of  Insects.     2  vols.     234-620  pp.,  133  figs.     London. 
Miiller,    F.     1864.     Fiir    Darwin.     Leipzig.     Trans. :    1869.     W.    S.    Dallas. 

l'"acts  and  Figures  in  aid  of  Darwin.     London. 
Brauer,  F.     1869.     Betrachtungen  fiber  die  Verwandlung  der  Insekten   im 

Sinne  der  Descendenz-Theorie.     Varh.  zool.-bot.  Gcsell.  Wien,  bd. 

19.  pp.  299-318;  bd.  28  (1878),  1879,  pp.  151-166. 
Lubbock,   J.     1873.     On   the   Origin   of   Insects.     Journ.    Linn.    Soc.    Zool, 

vol.  II,  pp.  422-425. 
Packard,  A.  S.     1873.     Our  Common   Insects.     225  pp.,  268  figs.     Boston. 

Estes  &  Lauriat. 
Lubbock,  J.     1874.     On  the   Origin  and  Metamorphoses  of  Insects.     164- 

108  pp.,  63  figs.,  6  pis.     London.     Macmillan  &  Co.* 
Mayer,  P.     1876.     Lfeber  Ontogenie  und  Phylogenie  der  Insekten.     Jenais. 

Zeits.   Naturw.,  bd.   10,  pp.   125-221,  taf.  6-6c. 
Wood-Mason,   J.     1879.     Morphological    Notes   bearing   on    the    Origin    of 

Insects.     Trans.  Ent.  Soc.  London,  pp.  145-167,  figs.  1-9. 
Haase,  E.     1881.     Beitrag  zur  Phylogenie  und  Ontogenie  der  Chilopoden. 

Zeits.  Ent.  Breslau,  bd.  8,  heft  2,  pp.  93-115. 
Lankester,  E.  R.     1881.     Limulus  an  Arachnid.     Quart.  Journ.    Micr.   Sc, 

vol.  21    (n.  s.),  pp.  504-548,  609-649,  pis.  28.  29,  figs.   1-20. 
Packard,  A.  S.     1881.     Scolopendrella  and  its   Position  in  Nature.     Amer. 

Nat.,  vol.   15,  pp.  698-704,  fig.  I. 
Kingsley,  J.   S.      1883.      Is   the   Group   Arthropoda   a   valid   one?      Amer. 

Xat.,  vol.  17,  pp.   1034-1037. 
Packard,  A.  S.     1883.     The  Systematic  Position  of  the  Orthoptera  in  rela- 
tion to  Other  Orders  of  Insects.     Third  Rept.  LI.  S.  Ent.  Comm., 

pp.  286-304. 
Brauer,   F.     1885.     Systematisch-zoologische    Studien.     Sitzb.    Akad.    Wiss. 

Wien,  bd.  91,  PP-  237-413.* 
Grassi,  B.     1885.     I  progenitori  degli  Insetti  e  dei  Mi.riapodi. — Morfologia 

delle   Scolopendrelle.     Atti.  Accad.  Torino,  t.  21,  pp.  48-50. 
Haase,  E.     1886.     Die  Vorfahren  der  Insecten.     Sitzb.  Abh.   Isis  Dresden, 

pp.  85-91. 
Claus,  C.     1887.     On   the  Relations  of   the   Groups   of   Arthropoda.     Ann. 

'Slag.  Nat.  Hist.,  ser.  5,  vol.   19,  p.  396. 
Kingsley,  J.  S.     1888.     The  Classification  of  the  Myriapoda.     Amer.  Nat., 

vol.  22,  pp.  1118-1121. 


412  ENTOMOLOGY 

Haase,  E.     1889.     Die   Abdominalanhjinge   der   Insekten  mit   Beriicksichti- 

gung   der   ]\Iyriopoden.     Morpli.    Jalirb.,   bd.    15,   pp.    331-435,   taf. 

14,   15- 
Fernald,    H.    T.     1890.     The   Relationships    of    Arthropods.     Studies    Biol. 

Lab.  Johns  Hopk.  Univ.,  vol.  4,  pp.  431-513,  pis.  48-50. 
Hyatt,  A.,  and  Arms,  J.  M.      1890.      Insecta.      23 -|- 300  pp.,    13  pis.,   223 

figs.     Boston.     D.    C.    Heath    &    Co.* 
Cholodkowsky,  N.     1892.     On  the  Morphology  and   Phylogeny  of  Insects. 

Ann.  Mag.  Nat.  Hist.,  ser.  6,  vol.  10,  pp.  429-451. 
Grobben,   C.     1893.     A  Contribution  to  the  Knowledge  of  the  Genealogy 

and   Classification  of  the   Crustacea.     Ann.   Mag.   Nat.   Hist.,   ser. 

6,   vol.    II,   pp.   440-473.     Trans,    from   Sitzb.   Akad.    Wiss.   Wien, 

math.-nat.  CI.,  bd.  loi,  heft  2,  pp.  237-274,  taf.   i. 
Hansen,    H.   J.     1893.     A   Contribution   to   the   Morphology   of   the    Limbs 

and    Mouth-parts   of    Crustaceans    and    Insects.     Ann.    Mag.    Nat. 

Hist.,   ser.   6,  vol.    12,  pp.  417-434.     Trans,   from   Zool.   Anz.,  jhg. 

16,  pp.   193-198,  201-212. 
Pocock,  R.  I.     1893.     On  some  Points  in  the  Morphology  of  the  Arachnida 

(s.  s.)   with  Notes  on  the  Classification  of  the  Group.     Ann.  Mag. 

Nat.  Hist.,  ser.  6,  vol.  11,  pp.  1-19,  pis.  i,  2. 
Pocock,  R.  I.     1893.     On  the   Classification  of  the   Tracheate   Arthropoda. 

Zool.  Anz.,  jhg.  16,  pp.  271-275. 
Bernard,  H.  M.     1894.     The  Systematic  Position  of  the  Trilobites.     Quart. 

Journ.  Geol.   Soc.  London,  vol.  50,  pp.  411-434,  figs.   1-17. 
Kingsley,    J.    S.      1894.      The    Classification    of    the    Arthropoda.     Amer. 

Nat.,  vol.  28,  pp.   118-135,  220-235.* 
Kenyon,  F.   C.     1895.     The   Morphology   and   Classification   of  the   Pauro- 

poda,   with    Notes   on   the   Morphology   of   the    Diplopoda.     Tufts 

Coll.  Studies,  no.  4,  pp.  77-146,  pis.   1-3. 
Schmidt,    P.      1895.      Beitrage    zur    Kenntnis    der    niederen    Myriapoden. 

Zeits.  wiss.  Zool.,  bd.  59,  pp.  436-510,  taf.  26,  27. 
Wagner,   J.      1895.      Contributions    to    the    Phylogeny    of    the    Arachnida. 

Ann.   Mag.   Nat.   Hist.,   ser.  6,  vol.   15,  pp.   285-315.     Trans,   from 

Jenais.  Zeits.  Naturw.,  bd.  29,  pp.  123-156. 
Miall,  L.  C.     1895.     The  Transformations  of  Insects.     Nature,  vol.  53,  pp. 

152-158. 
Sedgwick,  A.     1895.     Peripatus.     Camb.   Nat.   Hist.,  vol.   5,  pp.    1-26,   figs. 

1-14. 
Sinclair,   F.   G.     1895.     Myriapoda.     Camb.    Nat.   Hist.,   vol.   5,   pp.    27-80, 

figs.  15-46. 
Sharp,  D.     1895,   1901.     Insects.     Camb.   Nat.  Hist.,  vols.  5,  6.     12-1-1130 

pp.,  618  figs.     London   and  New  York.     Macmillan  &  Co.* 
Comstock,  J.  H.  and  A.  B.     1895.     A  Manual   for  the  Study  of   Insects. 

7  -|-  701  pp.,  797  figs.,  6  pis.     Ithaca,  N.  Y.     Comstock  Pub.  Co. 
Heymons,    R.      1896.      Zur    Morphologic    der    Abdominalanhange   bei    den 

Insecten.     Morph.  Jahrb.,  bd.  24,  pp.   178-204,   i   taf. 


LITERATURE  4I3 

Heymons,    R.      1897.      Mittheilungen    ul)ei-    die    Segmentierung    und    den 

Kr)rpcrbau   der   ]\Iyriopoden.     Sitzb.   Akad.   Wiss.,   Berlin,   bd.   40, 

pp.  9i5-9-'3.  2  figs. 
Hansen,  H.  J.,  and  Sorensen,  W.     1897.     The  Order  Palpigradi  Thor.  and 

its  Relationship  lo  the   Arachnida.     Knt.  Tidsk.,  arg.   18,  pp.  223- 

240,  pi.  4. 
Button,  F.  W.,  and  others.     1897.     Are  the  Arthropoda  a  Natnral  Gronp? 

Nat.  Sc,  \nl.  10,  p\i.  97-1 1/- 
Lankester,  E.   R.      1897.      Are   the   Arthropoda   a   Natnral    Gronp?      Nat. 

Sc,  vol.   ID,  pp.  264-268. 
Packard,  A.   S.     1898.     A   Text-Book  of   Entomology.     17  +  729  pp.,   654 

figs.     New  York  and  London.     The   IMacmillan   Co.* 
Packard,    A.     S.     1899.     Entomology      for     Beginners.     Ed.     3.     16  +  367 

pp..  273  figs.     New  York.     Henry  Holt  &  Co.* 
Von    Zittel,    K.    A.      1900,    1902.      Text-Book    of    Palaeontology.      2    vols. 

Trans.      C.    R.    Eastman.      London    and    New    York.      Macmillan 

&  Co.* 
Folsom,  J.  W.     1900.     The  Development  of  the   Month   Parts  of  Anurida 

maritima  Gner.     Bull.   Alus.   Comp.  Zool.,  vol.  36,  pp.  87-157,  pis. 

i-S.* 
Hansen,  H.  J.     1902.     On  the  Genera  and  Species  of  the  Order  Panropoda. 

\"idensk.   Mcdd.   Natnrh.  Foren.  Kjobenhavn    (1901),  pp.  323-424, 

pis.   1-6. 
Carpenter,  G.  H.     1903.     On  the  Relationships  between  the  Classes  of  the 

Arthropoda.     Proc.  R.  Irish  Acad.,  vol.  24,  pp.  320-360,  pi.  6* 
Enderlein,  G.     1903.     Ueber  die  Morphologie,  Gruppierung  und  systemat- 

ische    Stellung    der    Corrodentien.      Zool.    Anz.,    bd.    26,   pp.    423- 

437,  4  figs. 
Hansen,   H.  J.     1903.     The   Genera   and    Species   of   the   Order   Symphyla. 

Quart.  Journ.  INIicr.  Sc,  vol.  47,  pp.  i-ioi,  pis.  1-7. 
Packard,  A.  S.     1903.     Hints  on  the  Classification  of  the  Arthropoda;  the 

Group,  a   Polyphyletic  One.     Proc.   Amer.   Phil.   Soc,  vol.  42,  pp. 

142-161. 
Lankester,  E.  R.     1904.     The   Structure  and   Classification  of  the  Arthro- 
poda.    Quart.   Journ.    Micr.   Sc,   vol.   47    (n.    s.),   pp.   523-582,   pi. 

42.     (From  Encyc.  Britt.,  ed.  10.) 
Carpenter,  G.  H.     1905.     Notes  on  the  Segmentation  and  Phylogeny  of  the 

Arthropoda,   with  an  Account  of  the  Maxillse  in  Polyxenus  lag- 

urus.     Quart.  Journ.  Micr.  Sc,  vol.  49,  pt.  3,  pp.  469-491,  pi.  28.* 

GENERAL   ANATOMY 

De   Reaumur,   R.   A.   F.     1734-42.     Memoires   pour   servir   a   I'histoire   des 

insectes.     7  vols.     Paris. 
Lyonet,   P.     1762.     Traite   anatomique   de   la   Chenille,   qui    rouge   le   Bois 

de  Saule.     Ed.  2.     22 -f  616  pp.,  x8  pis.     La  Haye. 
Straus-Diirckheim,    H.      1828.      Considerations    generates    sur    I'anatomie 

comparee  des  aniniaux  articules,  etc.     19-1-434  PP-  10  pis.     Paris. 


414  ENTOMOLOGY 

Newport,  G.  1839.  Insecta.  Todd's  Cyclopaedia  Anat.  Phys.,  vol.  2,  pp. 
853-994,  figs.  329-439- 

Leydig,  F.  1851.  Anatomisches  nnd  Histologisches  iiber  die  Larve  von 
•  Corethra  plumicornis.  Zeits.  wiss.  Zool.,  bd.  3,  pp.  435-451,  taf. 
16,  iigs.   1-4. 

Leydig,  F.  1855.  Zum  feineren  Ban  der  Arthropoden.  Miiller's  Archiv 
Anat.  Phys.,  pp.  376-480,  taf.  3. 

Leydig,  F.  1857.  Lehrbuch  der  Histologic  des  Menschen  und  der  Thiere. 
124-551  pp.,  figs.     Frankfurt. 

Leydig,  F.  1859.  Zur  Anatomic  der  Insectcn.  Miiller's  Archiv  Anat. 
Phys.,  pp.  33-89,  149-183,  taf.  3. 

Leydig,  F.     1864.     Vom  Ban  des  tierischen  Korpers.     Tiibingen. 

Huxley,  T.  H.  1877.  A  Manual  of  the  Anatomy  of  Invcrtebrated  Ani- 
mals. London.  J.  and  A.  Churchill.  1878.  New  York.  D. 
Appleton  &  Co. 

Packard,  A.  S.,  and  Minot,  C.  S.  1878.  Anatomy  and  Embryology  [of 
the  locust].  First  Rept.  U.  S.  Ent.  Comm.,  pp.  257-279,  figs. 
12-18.     Washington. 

Lubbock,  J.  1879.  On  the  Anatomy  of  Ants.  Trans.  Linn.  Soc.  Zool., 
sen  2,  vol.  2,  pp.  141-154,  pis. 

Riley,  C.  V.,  Packard,  A.  S.,  and  Thomas  C.  1880,  1883.  Second  and 
Third  Repts.  U.  S.  Ent.   Comm.     Washington. 

Minot,  C.  S.  1880.  Histology  of  the  Locust  (Caloptenus)  and  the  Cricket 
(Anabrus).  Second  Rept.  V.  S.  Ent.  Comm.,  pp.  183-222,  pis. 
2-8.     Washington. 

Brooks,  W.  K.  1882.  Handbook  of  Invertebrate  Zoology,  pp.  237-269, 
figs.  129-141.     Boston.     S.  E.  Cassino. 

Viallanes,  H.  1882.  Rechcrches  sur  I'histologic  des  insectes.  Ann.  Sc. 
nat.  Zool.,  ser.  6,  t.  14,  pp.  1-348,  pis.   1-18. 

Leydig,  F.  1883.  Untersuchungen  zur  Anatomic  und  Histologic  der 
Thiere.     174  pp.,  8  taf.     Bonn. 

Miall,  L.  C,  and  Denny,  A.  1886.  The  Structure  and  Life-history  of  the 
Cockroach.  6 -(- 224  pp.,  125  figs.  London,  Lovell  Reeve  & 
Co. ;  Leeds,  R.  Jackson. 

Schaeffer,  C.  1889.  Beitrage  zur  Histologic  der  Lisektcn.  Zool.  Jahrb., 
]\Iorph.  Abth..  bd.  3,  pp.  611-652,  taf.  29,  30. 

Lowne,  B.  T.  1890-92.  The  Anatomy,  Physiology,  Morphology  and  De- 
velopment of  the  Blow-fly  (Calliphora  crythroccphala).  A  Study 
in  the  Comparative  Anatomy  and  Morphology  of  Insects.  8  4- 
778  pp.,  108  figs.,  21  pis.     London.* 

Lang,  A.  1891.  Text-Book  of  Comparative  .\natomy.  Trans,  by  H.  M. 
and  M.  Bernard.  Pt.  i,  pp.  43S-508,  figs.  301-356.  London  and 
New  York.     Macmillan  &  Co.* 

Comstock,  J,  H.,  and  Kellogg,  V.  L.  1899.  The  Elements  of  Insect  Anat- 
omy. Rev.  ed.  134  pp.,  11  figs.  Ithaca,  N.  Y.  Comstock  Pub- 
lishing Co. 


LITERATURE  4^5 


HEAD    AND    APPENDAGES 


Schaum,  H.     1863.     Uber  die  Ziisammensetzung  des  Kopfes  und  die  Zahl 

del-   Alxloniinalsegmente   bci   den   Insekten.     Archiv    Naturg.,   jhg. 

29,  1)(I.   I.  pp.  247-260. 
Basch,    S.     1865.     Skclctt   und    iNInskcln    des    Kopfes    von   Termes.     Zeits. 

wiss.  Zool.,  b(l   15,  pp.  55-/5,   i  t^f- 
Breitenbach,   W.      1877.      Vorlaiifige    Mitteilung   uber   einige   ncuc   Unter- 

suchungen  an  Schmetterlingsriisseln.     Arcbiv  mikr.  Anat.,  bd.   14, 

pp.  308-317.  I   taf. 
Breitenbach,    W.     1878.     Unter.sucbungen    an    Scbmetterlingsriisseln.     Ar- 

cliiv  mikr.  Anat.,  bd.   15,  pp.  8-29,  i   taf. 
Breitenbach,  W.     1879.     Ueber  Schmetterlingsriissel.     Ent.   Nachr.,  jbg.  5, 

pp.  237-243. 
Burgess,  E.     1880.     Contributions  to  tbe  Anatomy  of  tbc  Milk-weed  But- 

terBy    (Danais   arcbippus   Fabr.).     Anniv.    Mem.    Bost.    Soc.    Nat. 

Hist.,  16  pp.,  2  pis. 
Meinert,  F.     1880.     Sur  la  conformation  de  la  tete  et  sur  I'interpretation 

des  organes  buccaux  cbez  les  Insectes,  ainsi  que  sur  la  systema- 

tique  de  cet  ordre.     Ent.  Tidsk.,  arg.   i,  pp.   147-150. 
Dimmock,  G.     1881.     The  Anatomy  of  the  jNIouth  Parts  and  of  the  Suck- 
ing   Apparatus    of    some    Diptera.      50   pp.,    4    pis.      Boston.      A. 

Williams  &  Co.* 
Geise,  0.     1883.     Die   Mundtheile   der  Rbynchoten.     Archiv    Naturg.,   jbg. 

49,  bd.  I,  pp.  315-373.  taf.  10. 
Kraepelin,   K.      1S83.      Zur    Anatomic    und    Physiologic    des    Riissels    von 

jMusca.     Zeits.  wiss.  Zool,  bd.  39,  pp.  683-719,  taf.  40,  41. 
Briant,  T.  J.     1884.     On  the  Anatomy  and  Functions  of  the  Tongue  of  the 

Honey  Bee   (worker).     Journ.  Linn.  Soc.  Zool.,  vol.   17,  pp.  408- 

417,  pis.  18,  19. 
Wedde,    H.     1885.     BeitrJige    zur    Kenntniss    des    Rhynchotenriissels.     Ar- 
chiv Naturg.,  jhg.  51,  bd.   i,  pp.   1 13-143,  taf.  6,  7. 
Walter,  A.     1885.     Beitrage  zur  Morphologic  der  Schmetterlinge.     Jenais. 

Zeits.  Naturw.,  bd.  18,  pp.  751-807,  taf.  23,  24. 
Walter,     A.       1885.       Zur     Morphologic     der     Schmetteflingsmundtheile. 

Jenais.  Zeits.  Naturw.,  bd.   19,  pp.  19-27. 
Breithaupt,    P.    F.     1886.     Ueber    die    Anatomic    und    die    Functionen    der 

Bienenzunge.     Archiv  Naturg.,  jhg.  52,  bd.  i,  pp.  47-112,  taf.  4,  5.* 
Blanc,  L.     1891.     La  tete  du   Bombyx  mori  a  I'etat  larvaire,  anatomic  et 

physiologic.     Trav.    Lab.    fitud.    Soie,    1889-1890,    180  pp.,   95   figs. 

Lyon. 
Smith,  J.  B.     1892.     The  Mouth  Parts  of  Copris  Carolina;  with  Notes  on 

the  Homologies  of  the  Mandibles.     Trans.   Amer.   Ent.   Soc,  vol. 

19,  pp.  83-87,  pis.  2,  3. 
Hansen,   H.  J.     1893.     A   Contribution  to  the   Morphology   of   the   Limbs 

and  Mouth   Parts  of  Crustaceans  and  Insects.     Ann.   Mag.   Nat. 

Hist.,   ser.   6,  vol.    12,  pp.  417-434.     Trans,   from   Zool.   Anz.,  jhg. 

16,  pp.  193-198,  201-212. 


41 6  ENTOMOLOGY 

Kellogg,  V.  L.     1895.     Tlie  ]\Iouth  Parts  of  the  Lepidoptera.     Amer.  Nat.. 

vol.    29,    pp.    546-556,    pi.    25,    figs.    I,    2. 

Smith,  J.  B.     1896.     An  Essay  on  the   Development  of  the   Mouth   Parts 

of  certain   Insects.     Trans.   Amer.   Phil.   Soc,  vol.   19    (n.   s.),  pp. 

175-198,  pis.  1-3. 
Folsom,  J.  W.     1899.     The  Anatomy  and  Physiology  of  the  Mouth   Parts 

of  the  Collembolan,  Orchesella  cincta  L.     Bull.  Mus.  Comp.  Zool., 

vol.  35,  pp.  7-39,  pis.   1-4.* 
Janet,    C.     1899.     Essai   sur   la   constitution   morphologique   de   la   tete   de 

I'insecte.     74  pp.,  7  pis.     Paris.     G.  Carre  et  C.   Naud. 
Kellogg,   V.   L.     1899.     The   Mouth    Parts   of   the    Nematocerous    Diptera. 

Psyche,   vol.    8,    pp.    303-306,    327-220,    346-348,    355-359,    363-365, 

figs.    I-II. 
Folsom,  J.  W.     1900.     The  Development  of  the  Mouth  Parts  of  Anurida 

maritima  Guer.     Bull.  Mus.  Comp.  Zool.,  vol.  2i^,  pp.  87-157,  pis. 

1-8.* 
Comstock,  J.  H.,  and  Kochi,  C.     1902.     The  Skeleton  of  the  Head  of  In- 
sects.    Amer.  Nat.,  vol.  36,  pp.  13-45,  figs.  1-29.* 
Kellogg,  V.  L.     1902.     The   Development  and   Homologies  of  the   Mouth 

Parts  of  Insects.     Amer.   Nat.,  vol.  36,  pp.  683-706,  figs.   1-26. 
Meek,   W.   J.      1903.      On    the   Mouth    Parts   of   the    Hemiptera.      Kansas 

Univ.   Sc.   Bull,  vol.  2   (12),  pp.  257-277,  pis.  7-1 1.* 
Holmgren,  N.      1904.      Zur  Morphologic  des  Insektenkopfes.      Zeits.  wiss. 

Zool.,  bd.  76,  pp.  439-477,  taf.  27,  28.* 
Kulagin,  N.     1905.     Der  Kopfbau  bei  Culex  und  Anopl^eles.     Zeits.   wiss. 

Zool.,  bd.  83,  pp.  285-335,  taf.   12-14.* 

THORAX  AND  APPENDAGES;  LOCOMOTION 

Audouin,  J.  V.  1824.  Recherches  anatomiques  sur  le  thorax  des  animaux 
articules  ct  celui  des  insectes  hexapodes  en  particulier.  Ann.  Sc. 
nat.  Zool,  t.  I.  pp.  97-135,  416-432,  figs. 

MacLeay,  W.  S.  1830.  Explanation  of  the  comparative  anatomy  of  the 
thorax  in  winged  insects,  with  a  review  of  the  present  state  of 
the  nomenclature  of  its  parts.  Zool.  Journ.,  vol.  5,  pp.  145-179, 
2  pis. 

Langer,  K.  i860.  Ueber  den  Gelenkbau  bei  den  Arthrozoen.  Vierter 
Beitrag  zur  vergleichenden  Anatomic  und  Mechanik  der  Gelenke. 
Denks.  Akad.  Wiss.  Wien.,'Phys.  CL,  bd.   18,  pp.  99-140,  3  taf. 

"West,  T.  1861.  The  Foot  of  the  Fly;  its  Structure  and  Action;  eluci- 
dated by  comparison  with  the  feet  of  other  Insects,  etc.  Trans. 
Linn.  Soc.  Zool,  vol.  23,  pp.  393-421,  pis.  41-43. 

Plateau,  F.  1871.  Qu'est-ce  que  I'aile  d"un  Insecte?  Stett.  ent.  Zeit., 
jhg.  32,  pp.  33-42,  pi.  I. 

Plateau,  F.  1872.  Recherches  experimentales  sur  la  position  du  centre 
de  gravite  chez  les  insectes.  Archiv.  Sc.  phys.  nat.  Geneve,  nouv. 
per.,  t.  43,  pp.  5-37. 


LITERATURE  417 

Pettigrew,  J.  B.     1874.     Animal  Locomotion.     13  +  264  pp.,  130  figs.     New 

York.     D.  Appleton  &  Co. 
Marey,   E.  J.      1874,   1879.      Animal   Mechanism.      16  +  283   pp.,    117  figs. 

New  York.     D.  Appleton  &  Co. 
Hammond,  A.     1881.     On  the  Thorax  of  the  Blow-fly  (Musca  vomitoria). 

Journ.  T,inn.  Soc.  Zool.,  vol.  15,  pp.  9-31,  pls.   i,  2. 
Von  Lendenfeld,  R.     1881.     Der  Plug  der  Libellen.     Kin  Beitrag  zur  Anat- 
omic und  Physiologic  der  Plugorgane  der  Insecten.     Sitzb.  Akad. 

Wiss.  Wien.,  bd.  83,  pp.  289-376,  taf.  1-7. 
Brauer,  F.     1882.     Ueber  das   Segment  mediaire  Latrcillc's.     Sitzb.   Akad. 

\\'iss.  Wien,  bd.  85,  pp.  218-244,  taf.  1-3. 
Dahl,  F.     1884.     Beitriige  zur  Kenntnis  des  Baues  vmd  der  Fiinktionen  der 

Insektenbeine.     Archiv   Naturg.,   jhg.   50,  bd.    i,   pp.    146-193.   taf. 

II-I3- 
Dewitz,   H.     1884.     Ueber   die   Portbewegung   der   Thiere   an   senkrechten 

glattcn  I'liichen  vermittelst  eines  Sekretes.     Pflitger's  Archiv  ges. 

Phys.,  bd.  33,  pp.  440-481,  taf.   7-9. 
Graber,  V.     1884.     Ueber  die  Mechanik  des  Insektenkorpers.     L  Mechanik 

der  Peine.     Biol.  Centralbl.,  bd.  4,  pp.  560-570. 
Amans,  P.     1885.     Comparaisons  des  organes  du  vol  dans  la  serie  animale. 

Ann.  Sc.  nat.  Zool.,  sen  6,  t.  19,  pp.  1-222,  pis.  1-8. 
Redtenbacher,  J.     1886.     Vergleichende  Studien  iiber  das  Pliigelgeader  der 

Insecten.      Ann.    naturh.    Hofm.    Wien,    bd.    i.    pp.    153-232,    taf. 

9-20. 
Amans,   P.   C.     1888.     Comparaisons   des   organes   de   la   locomotion   aqua- 

tique.     Ann.  Sc.  nat.  Zool.,  ser.  7,  t.  6,  pp.  1-164,  pis.  1-6. 
Carlet,  G.     1888.     Sur  le  mode  de  locomotion  des  chenilles.     Compt.  rend. 

Acad.  Sc,  t.  107,  pp.  131-134- 
Ockler,    A.     1890.     Das    Krallenglied    am    Insektenfuss.     Archiv    Naturg., 

jhg.  56,  bd.  I,  pp.  221-262,  taf.  12,  13. 
Demoor,  J.     1891.     Recherches  sur  la  marche  des  Insectes  et  des  Arach- 

nides.     Archiv.   Biol.,  t.   10,  pp.  567-608,  pis.   18-20. 
Hoffbauer,    C.     1892.     Beitrage    zur    Kenntnis    der    Insektenfliigel.     Zeits. 

wiss.  Zool;.  bd.  54,  pp.  579-630,  taf.  26,  27,  3  figs.* 
Spuler,  A.     1892.     Zur   Phylogenie  und   Ontogenie  des   Pliigelgeader  der 

Schmetterlinge.     Zeits.  wiss.  Zool.,  bd.  53,  pp.  597-646,  taf.  25,  26. 
Comstock,    J.    H.      1893.      Evolution    and    Taxonomy.      Wilder    Quarter- 

Centurj'  Book,  pp.  37-114,  pls.  i-3-     Ithaca,  N.  Y. 
Kellogg,  V.  L.     1895.     The  Affinities  of  the  Lepidopterous   Wing.     Amer. 

Nat.,  vol.  29,  pp.  709-717,  figs.   i-io. 
Marey,  E.  J.     1895.     Movement.     15  +  3^3  PP-,  204  figs.     New  York.     D. 

Appleton  &  Co. 
Comstock,  J,  H.,  and   Needham,  J.   G.     1898-99.     The   Wings   of   Insects. 

Amer.  Nat.,  vols.  32,  33,  pp.  43-48,  81-89,  231-257,  335-340,  413- 

424,  561-565,  769-777,  903-911,  117-126,  573-582,  845-860,  figs.  1-90. 

Reprint,  Ithaca,  N.  Y.     Comstock  Pub.  Co. 
Walton,  L.  B.     1900.     The  Basal  Segments  of  the  Hexapod  Leg.     Amer. 

Nat.,  vol.  34,  pp.  267-274,  figs.  1-6. 


41 «  ENTOMOLOGY 

Verhoeff,  K.  W.  1902.  Beitrage  zur  vergleichenden  Morphologic  des 
Thorax  der  Insekten  mit  Beriicksichtigung  der  Chilopoden.  Nova 
Acta  Leop. -Carol.  Akad.  Naturf.,  bd.  81,  pp.  63-110,  taf.  7-13. 

Voss,  F.  1904-05.  Uber  den  Thorax  von  Gryllus  domesticus.  Zcits. 
wiss.  Zool.,  bd.  78,  pp.  268-521,  taf.   15,   16,  25  figs. 

ABDOMEN    AND   APPENDAGES 

Lacaze-Duthiers,   H.     1849-53.     Rechcrches   sur   Tarmure  genitalc   femelle 

des   insectes.     Ann.   Sc.   nat  Zool.,   ser.  3,   t.    12-19,   pls.     Several 

papers. 
Fenger,    W.    H.     1863.     Anatomic   nnd    Physiologic    des    Giftapparates    bei 

den  Hymenopteren.     Archiv  Naturg.,  jhg.  29,  bd.   i,  pp.   139-178, 

I  taf. 
Schaum,  H.     1863.     Ueber  die  Zusammensetziing  des  Kopfes  und  die  Zahl 

der  Abdominalsegmente  bei   den  Insekten.     Archiv   Naturg.,   jhg. 

29,  bd.  I,  pp.  247-260. 
Sollmann,    A.     1863.     Der   Bienenstachel.     Zeits.    wiss.    Zool.,    bd.    13,    pp. 

528-540,  I  taf. 
Packard,  A.  S.     1866.     Observations  on  the  Development  and  Position  of 

the    Hymenoptera,    with    Notes    on    the    Morphology    of    Insects. 

Proc.  Bost.  Soc.  Nat.  Hist.,  vol.  10,  pp.  279-295,  figs.  1-4. 
Goossens,    T.     1868.     Notes    sur    les   pattes    membraneuses    des    Chenilles. 

Ann.  Soc.  ent.   France,  ser.  4,  t.  8,  pp.  745-748. 
Packard,  A.   S.     1868.     On  the  Structure  of  the   Ovipositor  and  Homol- 
ogous Parts  in  the  Male  Insect.     Proc.  Bost.  Soc.  Nat.  Hist.,  vol. 

II,  pp.  393-399,  figs.  i-ii. 
Graber,    V.     1870.     Die    Aehnlichkeit    im    Baue    der    ausseren    weiblichen 

Geschlechtsorgane   bei   den   Locustiden   und   Akridiern   dargestellt 

auf    Grund    ihrer    Entwicklungsgeschichte.     Sitzb.     Akad.     Wiss. 

Wien,  math.-naturw.  CL,  bd.  61,  pp.  597-616,  taf. 
Scudder,  S.  H.,  and  Burgess,  E.     1870.     On  Asymmetry  in  the  Appendages 

of  Hexapod  Insects,  especially  as  illustrated  in  the  Lepidopterous 

Genus  Nisoniades.     Proc.  Bost.  Soc.  Nat.  Hist.,  vol.   13,  pp.  282- 

306,  I  pi. 
Krapelin,  C.     1873.     Untersuchungen  iiber  den  Bau,  Mechanismus  und  die 

Entwicklungsgeschichte    des    Stachels    der    bienenartigen    Thiere. 

Zeits.  wiss.  Zool,  bd.  23,  pp.  289-330,  taf.   15,  16. 
Dewitz,   H.     1875.     Ueber   Bau   und    Entwickelung   des    Stachels   und    der 

Legescheide  einiger  Hymenopteren  und  der  grihien  Heuschrecke. 

Zeits.  wiss.  Zool.,  bd.  25,  pp.  174-200,  taf.  12,  13. 
White,  F.  B.     1876.     On  the  Male  Genital  Armature  in  the  Rhopalocera. 

Trans.  Linn.  Soc.  Zool.,  ser.  i,  vol.  i,  pp.  357-369,  3  pis. 
Adler,    H.     1877.    Lege-Apparat    und    Eierlegen    der    Gallwespen.     Deuts. 

ent.  Zeits.,  jhg.  21,  pp.  305-332,  taf.  2. 
Dewitz,  H.     1877.     Ueber  Bau  und  Entwickelung  des   Stachels  der  Amei- 

sen.     Zeits.  wiss.  Zool.,  bd.  28,  pp.  527-556,  taf.  26. 


LITERATURE  419 

Davis,  H.     1879.     Notes  on  the  Pygidia  and  Ccrci   of   Insects.     Jonrn.   R. 

INIicr.  Soc,  vol.  2,  pp.  252-255. 
Kraatz,    G.     1881.     Ueber   die    Wichtigkeit    der    Untcrsuclunig   des   miinn- 

lichen  Begattungsgliedes  der  Krifer  fur  die  Systcmatik  und  Artun- 

terscheidung.     Dents,    ent.   Zeits.,   jhg.   25,   pp.    113-126. 
Dewitz,  H.     1882.     Ueber  die  Fiihrung  an  den  Korperhiingen  der  Insecten. 

P.crlin  ent.  Zeits.,  bd.  26,  pp.  51-68,  fig. 
Gosse,   P.  H.     1882.     On  the   Clasping   Organs   ancillary  to   Generation   in 

certain  Groups  of  the  Lepidoptera.     Trans.  Linn.   Soc.  Zool,   ser. 

2,  vol.  2,  pp.  265-345,  8  pis. 
Von  Hagens,  D.     1882.     Ueber  die  mannlichen  Genitalien  der  Bienen-Gat- 

tung  Sphecodes.     Dents,  ent.  Zeits.,  jhg.  26,  pp.  209-228,  taf.  6,  7. 
Radoszkowski,  0.     1884.     Revision  des  armures  copulatrices  des  males  du 

genre  Bombus.     Bull.  Soc.  Nat.  Moscou,  t.  49,  pp.  51-92,  4  pls. 
Saunders,  E.     1884.     Further  notes  on  the  terminal  segments  of  Aculeate 

Hynienoptera.     Trans.   Ent.   Soc.  London,  pp.  251-267. 
Haase,  E.     1885.     Ueber  sexnelle   Charactere  bei   Schmetterlingen.     Zeits. 

Ent.  Breslau,  n.  f,  bd.  9.  PP-  15-19;  bd.  10,  pp.  36-44- 
Radoszkowski,  0.     1885.     Revision  des  armures  copulatrices  des  males  de 

la  famille  des   Mutillidje.     Horse  Soc.   Ent.   Ross.,  t.   19,  pp.  3-49. 

9  pis. 
Von  Ihering,  H.     1886.     Der  Stachel  der  Meliponen.     Ent.  Nachr.,  jhg.  12, 

pp.   177-188,  taf.  8. 
Goossens,  T.     1887.     Les  pattes  des  Chenilles.     Ann.  Soc.  ent.  France,  ser. 

6,  t.  7.  pp.  385-404.  pl-  7- 
Graber,  V.     1888.     Ueber  die  Polypodie  bei  Insekten-Embryonen.     Morph. 

Jahrb.,  bd.   13,  pp.  586-615,  taf.  25,  26. 
Haase,  E.     1889.     Ueber  Abdominalanhange  bei  Hexapoden.     Sitzb.  Gesell. 

naturf.  Freunde,  pp.  19-29. 
Haase,  E.     1889.     Die   Abdominalanhange   der  Insekten  mit   Beriicksichti- 

gung   der   Myriopoden.     Morph.   Jahrb.,   bd.    15,   pp.    331-435.   taf. 

14,   15. 
Radoszkowski,  0.     1889.    Revision  des  armures  copulatrices  des  males  de 

la  tribu  des  Chrysides.     Horse  Soc.  Ent.  Ross.,  t.  23,  pp.  3-40,  pis. 

1-6. 
Beyer,  0.  W.     1890.     Der  Giftapparat  von   Formica   rufa,   ein   reduziertes 

Organ.     Jenais.  Zeits.  Naturw.,  bd.  25,  pp.  26-112,  taf.  3,  4. 
Carlet,  G.     1890.     Memoire   sur   le  venin  et   I'aiguillon   de   I'abeille.     Ann. 

Sc.  nat.  Zool.,  ser.  7,  t.  9,  pp.  1-17,  pi.   i. 
Packard,   A.   S.     1890.     Notes   on    some   points    in    the    external    structure 

and   phylogeny    of   Lepidopterous    larvse.     Proc.    Bost.    Soc.    Nat. 

Hist.,  vol.  25,  pp.  S2-114,  pis.  I,  2. 
Sharp,  D.     1890.     On  the  structure  of  the  terminal  segment  in  some  male 

Hemiptera.     Trans.   Ent.   Soc.  London,  pp.  399-427,  pis.   12-14. 
Wheeler,  W.  M.     1890.     On  the  Appendages  of  the  first  abdominal   Seg- 
ment of  embryo   Lisects.     Trans.  Wis.   Acad.   Sc,  vol.  8,  pp.  87- 

140,  pis.   1-3.* 


420  ENTOMOLOGY 

Escherich,   K.     1892.     Die   biologische   Bedeutung   der   Genitalanhange   der 

Insektcn.     Verb,  zool.-bot.   Ges.  Wien,  bd.  42,  pp.  225-240,  taf.  4. 
Graber,  V.     1892.     Ueber  die  morphologische  Bedeutung  der  Abdominalan- 

bange  der  Insekten-Embrvonen.     Alorpb.  Jabrb.,  bd.   17,  pp.  467- 

482. 
Escherich,   K.     1894.     Anatomiscbe    Studien   iiber   das   mannUcbe   Genital- 
system   der   Coleopteren.     Zeits.    wiss.    Zool.,   bd.   57,   pp.   620-641, 

taf.  26,  3  figs. 
Janet,    C.     1894.     Sur    la    Morphologie    du    squelette    des    segments    post- 

thoraciques  chez  les  Myrmicides.     Note  5.     Mem.  Soc.  acad.  Oise, 

t.  15,  pp.  591-61 1,  figs.  1-5. 
Perez,  J.     1894.     De  I'organe  copulateur  male  des  Hymenopteres  et  de  sa 

valeur  taxonomique.     Ann.  Soc.  ent.  France,  t.  63,  pp.  74-81,  figs. 

1-8. 
Verhoeff,   C.     1894.     Vergleicbende    Untersucbungen   iiber   die   Abdominal- 

segmente  der  weiblichen  Hemiptera-Heteroptera  und  Homoptera. 

Verb.  nat.  Ver.  Bonn,  jhg.  50,  pp.  307-374. 
Heymons,  R.     1895.     Die   Segmentirung  des   Insectenkorpers.     Anb.   Abb. 

Preuss.  Akad.  Wiss.  Berlin,  39  pp.,  i  taf. 
Heymons,    R.     1895.     Die    Embryonalentwickelung   von    Dermapteren   und 

Ortbopteren  unter  besonderer  Beriicksicbtigung  der  Keimblatter- 

bildung.     136  pp.,   12  taf.,  33  figs.     Jena. 
Peytoureau,   S.   A.      1895.      Contribution  a  I'etude   de   la  morpbologie   de 

I'armure  genitale  des  Insectes.     248  pp.,  22  pis.,  43  figs.     Paris. 
Verhoeff,   S.     1895.     Beitrage  zur  vergleicbenden  Morpbologie  des  Abdo- 
mens der  Coccinelliden,   etc.     Arcbiv   Naturg.,  jbg.  61,  bd.   i,  pp. 

1-80,  taf.   1-6. 
Verhoeff,     C.     1895.     Vergleicbend-morpbologiscbe     Untersucbungen     iiber 

das    Abdomen    der    Endomychiden,    Erotyliden    und    Languriiden 

(im   alten   Sinne)    und   iiber  die   Muskulatur  des   Copulationsap- 

parates  von  Triplex.     Arcbiv  Naturg.,  jbg.  61,  bd.   i,  pp.  213-287, 

taf.  12,  13. 
Verhoeff,    C.     1895.     Cerci    und    Styli    der   Tracbeaten.     Ent.    Nacbr.,    jhg. 

21.  pp.  166-168. 
Heymons,  R.     1896.     Grundziige   der   Entwickelung  und   des   Korperbaues 

von  Odonaten  und  Ephemeriden.     Anb,  Abb.  Akad.  Wiss.  Berlin, 

66  pp.,  2  taf. 
Heymons,    R.     1896.     Zur    Morphologie    des    Abdominalanhange    bei    den 

Insekten.     Morpb.  Jabrb.,  bd.  24,  pp.    178-204,  taf.   i. 
Verhoeff,    C.     1896.     Zur    Morphologie    der    Segmentanbange    bei    Insecten 

und  Myriopoden.     Zool.   Anz.,  bd.   19,  pp.  378-383,  385-388. 
Goddard,  M.  F.     1897,     On  the  Second  Abdominal  Segment  in  a  few  Libel- 

lulidse.     Proc.  Amer.   Phil.   Soc,  vol.  35,  pp.  205-212,  2  pis. 
Janet,  C.     1897.     Limites  morphologiques  des  anlieaux  post-cephaliques  et 

Musculature  des  anneaux  post-thoraciques  chez  la  Myrmica  rubra. 

Note  16.     35  pp.,  10  figs.     Lille. 
Verhoeff,    C.     1897.     Bemerkungen    iiber    abdominale    Korperanhange    bei 

Insecten  und  Myriopoden.     Zool.   Anz.,  bd.  20,  pp.  293-300. 


LITERATURE  42 1 

Janet,  C.  1898.  Aignillon  de  la  ]\Iyrmica  rubra.  Appareil  dc  fcrmeture 
de  la  glande  a  venin.     Note  18,     27  pp.,  3  pis.     Paris. 

Zander,  E.  1903.  Bcitriige  zur  Morphologic  der  mannlichen  Geschlechts- 
anhange  der  Lepidopteren.  Zcits.  wiss.  Zool.,  bd.  74,  pp.  557- 
615,  taf.  29,  figs.  1-15.* 


INTEGUMENT 

Dufour,   L.     1824-26.     Recbcrches   anatomiques   siir   les   Carabiques   et   sur 

plusieurs    autres    Coleopteres.      Ann.    Sc.    nat.    ZooL,    t.    2-8,    pis. 

Several  papers. 
Karsten,    H.      1848.      Harnorgane    des    Brachinus    complanatus.      Miiller's 

Archiv  Anat.  Phys.,  pp.  367-374,  fig- 
Leydig,  F,     1855.     Zum  feineren   Ban   der  Arthropodcn.     Miiller's   Archiv 

Anat.   Phys.,  pp.  376-480,  taf.  3- 
Semper,  C.     1857.     Beobachtungen  iiber  die  Bildung  der  Fliigcl,  Schuppen 

und   Haare   bei    den   Lepidopteren.     Zeits.   wiss.    Zool,   bd.    8,   pp. 

326-339.  taf.  IS. 
Sirodot,  S.     1858.     Recherches  sur  les  secretions  chez  les  Insectes.     Ann. 

Sc.  nat.  ZooL,  ser.  4,  t.  10,  pp.  141-189,  251-334,   12  pis. 
Claus,    C.      1861.     Ueber    die    Seitendriisen    der    Larve    von    Chrysomela 

populi.     Zeits.  wiss.  Zool.,  bd.  11,  pp.  309-314,  taf.  25. 
Landois,    H.     1864.     Beobachtungen    iiber    das    Blut    der    Insecten.     Zeits. 

wiss.  Zool.,  bd.  14,  pp.  55-70,  taf.  7-9. 
Landois,   H.     1871.     Beitrage   zur   Entwicklungsgeschichte   der   Schmetter- 

lingsflugel   in   der  Raupe   und    Puppe.     Zeits.   wiss.   Zool.,   bd.   21, 

pp.  305-316,  taf.  23. 
Candeze,  E.     1874.     Les  moyens  d'attaque  et  de  defense  chez  les  Insectes.. 

Bull.  Acad.  roy.  Belgique,  ser.  2,  t.  38,  pp.  787-816. 
Chun,   C.      1876.      Ueber   den   Bau,    die   Entwickelung   und   physiologische 

Bedeutung   der  Rektaldriisen   bei   den   Insekten.     Abb.    Senckenb. 

naturf.  Gesell.,  bd.   10,  pp.  27-55,  4  taf.     Separate,  1875,  31  pp.,  4 

taf.     Frankfurt  a.    M. 
Miiller,  F.     1877.     Ueber  Haarpinsel.  Filzflecke  und  ahnliche  Gebilde  auf 

den    Fliigeln    mannlicher    Schmetterlinge.     Jenais    Zeits.    Naturw., 

bd.  II,  pp.  99-114- 
Scudder,   S.   H.      1877.      Antigeny   or    Sexual    Dimorphism    in    Butterflies. 

Proc.  Amer.  Acad.  Arts  Sc,  vol.  12,  pp.  150-158. 
Edwards,  W.  H.     1878.     On   the  Larvpe  of  Lye.  pseudargiolus   and   atten- 
dant Ants.     Can.   Ent.,  vol.   10,  pp.   131-136,  fig.  8. 
Forel,    A.      1878.      Der    Giftapparat    und    die    Analdriisen    der    Ameisen. 

Zeits.  wiss.  Zool.,  bd.  30,  supp.,  pp.  28-68,  taf.  3,  4. 
Miiller,   F.      1878.      Die    Duftschuppen    der    Schmetterlinge.     Ent.    Nachr., 

jhg.  4,  pp.  29-32. 
Saunders,  E.     1878.     Remarks  on  the  Hairs  of  some  of  our  British  Hy- 

menoptera.     Trans.    Ent.    Soc.   London,   pp.    169-172,   pi.   6. 


42  2  ENTOMOLOGY 

Schneider,  R.      1878.      Die   Schuppen   aus   den  verschiedenen  Fliigel-   und 

Korperteilen  der  Lepidopteren.     Zeits.  gesammt.  Naturw.,  bd.  51, 

pp.  1-59. 
Weismann,  A.     1878.     Ueber  Duftschuppen.     Zool.  Anz.,  jhg.  i,  pp.  98,  99. 
Goossens,  T.     1881.     Des  chenilles  urticantes,  etc.     Ann.   Soc.  ent.   France. 

t.  I,  pp.  231-236. 
Scudder,   S.   H.     1881.     Butterflies;    Their   Structure,   Changes   and   Life- 
Histories,,  with   Special  Reference  to  American   Forms.     9  -j-  2,22 

pp.,  201  figs.     New  York.     Henry  Holt  &  Co. 
Dimmock,  G.     1882.     On  some  Glands  which  open  externally  on   Insects. 

Psyche,  vol.  3,  pp.  387-401.* 
Klemensiewicz,  S.     1882.     Zur  naheren  Kenntniss  der  Hantdriisen  bei  den 

Raupen  und  bei  Malachius.     Verb.  zool. -hot.  Gesell.  Wien,  bd.  32, 

pp.  459-474,  2  taf. 
Dimmock,  G.     1883.     The  Scales  of  Coleoptera.     Psyche,  vol.  4,  pp.   i-ii, 

23-27,  43-47,  63-71,  figs.  i-ii. 
Osten-Sacken,  C.  R.     1884.     An  Essay  on  Comparative  Chaetotaxy,  or  the 

Arrangement   of   characteristic    Bristles   of   Diptera.     Trans.    Ent. 

Soc.  London,  pp.  497-517. 
Simmermacher,  G.     1884.     Untersuchungen  fiber  Haftapparate  an  Tarsal- 

gliedern  von  Insekten.     Zeits.  wiss.  Zool.,  bd.  40,  pp.  481-556,  taf. 

25-27,  2  figs. 
Dahl,   F.     1885.     Die   Fussdrusen   der   Insekten.     Archiv   mikr.   Anat.,   bd, 

25,  pp.  236-263,  taf.   12,  13. 
Witlaczil,  E.     1885.     Die  Anatomic  der   Psylliden.     Zeits.   wiss.   Zool.,  bd. 

42,  pp.  569-638,  taf.  20-22. 
Goossens,  T.     1886.     Des  chenilles  vesicantes.     Ann.  Soc.  ent.  France,  sen 

6,   t.   6,  pp.  461-464.* 
Minot,  C.  S.     1886.     Zur  Kenntniss  der  Insektenhaut.     Archiv  mikr.  Anat., 

bd.  28,  pp.  37-48,  taf.  7. 
Schaffer,   C.     1889.     Beitrage   zur   Histologic   der   Insekten.     Zool.   Jahrb., 

Abth.  Anat.  Ont.,  bd.  3,  pp.  611-652,  taf.  29,  30. 
Fernald,  H.  T,     1890.    Rectal  Glands  in  Coleoptera.     Amer.  Nat.,  vol.  24, 

pp.  100,  loi,  pis.  4,  5. 
Packard,  A.  S.     1890.     Notes  on  some  points  in  the  external  structure  and 

phylogeny  of  lepidopterous   larvae.     Proc.    Bost.    Soc.   Nat.    Hist., 

vol.  25,  pp.  82-114,  pis.  I,  2. 
Borgert,   H.     1891.     Die   Hautdriisen   der  Tracheaten.     81   pp..   taf.     Jena. 
Thomas,  M.  B.     1893.     The  Androconia  of  Lepidoptera.     Amer.  Nat.,  vol. 

27,  pp.  1018-1021,  pis.  22,  23. 
Cuenot,  L.     1894.     Le  rejet  de  sang  comme  nioyen  de  defense  chez  quel- 

ques  Coleopteres.     Compt.  rend.  Acad.  Sc,  t.  118,  pp.  875-877. 
Kellogg,  V.  L.     1894.     The  Taxonomic  Value  of  the  Scales  of  the  Lepidop- 
tera.    Kansas  Univ.  Quart.,  vol.  3,  pp.  45-89,  pis.  9,  10,  figs.  1-17. 
Packard,  A.  S.     1894.     A  Study  of  the  Transformations  and  Anatomy  of 

Lagoa  crispata,  a  Bombycine  Moth.     Proc.  Amer.  Phil.'  Soc,  vol. 

32,  pp.  275-292,  pis.   1-7. 


LITERATURE  423 

Lutz,  K.  G.      1895.      Das   Bluten   der  Coccinelliden.      Zool.   Anz.,   jhg.    18, 

pp.  244-255,   I   fig. 
Packard,  A.   S.     1895-96.     The   Eversible  Repugnatorial   Scent   Glands  of 

Insects.     Journ.  N.  Y.  Ent.  Soc,  vol.  3,  pp.  1 10-127,  pi.  5;  vol.  4, 

pp.  26-32.* 
Spuler,  A.     1895.     Beitrag  zur  Kenntniss  des  feineren  Baues  und  der  Phy- 

logenie    der    Fliigelbedeckung   der    Schmetterlinge.     Zool.    Jahrb., 

Abth.  Anat.  Ont.,  bd.  8,  pp.  520-543,  taf.  36. 
Mayer,  A.  G.     1896.     The  Development  of  the  Wing  Scales  and  their  Pig- 
ment in  Butterflies  and  Moths.     Bull.  Mus.  Comp.  Zool,  vol.  29, 

pp.  209-236,  pis.  1-7.* 
Bordas,    L.      1897.      Description    anatomique    et    etude    histologique    des 

glandes  a  venin  des  Insectes  hymenopteres.     53  pp.,  2  pis.     Paris. 
Cuenot,   L.      1897.      Sur  la  saignee   reflexe  et  les  moyens  de  defense  de 

quelques  Insectes.     Arch.  Zool.  exp.,  ser.  3,  t.  4,  pp.  655-680,  4  figs. 
Hilton,   W.   A.     1902.     The   Body   Sense    Hairs   of   Lepidopterous   Larvae. 

Amer.  Nat.,  vol.  36,  pp.  561-578,  figs.  1-23.* 
Tower,  W.  L.     1902.     Observations  on  the  Structure  of  the  Exuvial  Glands 

and  the  Formation  of  the  Exuvial  Fluid  in  Insects.     Zool.  Anz., 

bd.  25,  pp.  466-472,  figs.  1-8. 
Tower,  W.  L.     1903.     The  Development  of  the  Colors  and  Color  Patterns 

of  Coleoptera,  with  Observations  upon  the  Development  of  Color 

in  Other  Orders  of  Insects.     Univ.   Chicago,  Decenn.   Publ.,  vol. 

10,  140  pp.,  3  pis. 
Plotnikow,  W.     1904.     Uber   die   Hautung  und   iiber  einige   Elemente  der 

Haut  bei   den   Insekten.     Zeits.    wiss.   Zool.,   bd.   76,   pp.   333-3^6, 

taf.  21,  22,  2  figs. 

MUSCULAR    SYSTEM 
Lyonet,  P.     1762.     Traite  anatomique  de  la  Chenille,  qui  ronge  le  Bois  de 

Saule.     Ed.  2.     22 -f- 616  pp.,  18  pis.     La  Haye. 
Straus-Diirckheim,    H.      1828.      Considerations    generales    sur    I'anatomie 

comparee  des  animaux  articules,  etc.     434  pp.,   10  pis.     Paris. 
Newport,  G.     1839.     Insecta.     Todd's  Cyclopaedia  Anat.   Phys.,  vol.  2,  pp. 

853^94.  figs.  329-439- 
Lubbock,  J.     1859.     On  the  Arrangement  of  the  Cutaneous  Muscles  of  the 

Larva  of  Pygasra  bucephala.     Trans.  Linn.  Soc.  Zool,  vol.  22,  pp. 

163-191,  2  pis. 
Basch,   S.     1865.     Skelett  und    Muskeln   des   Kopfes   von   Termes.     Zeits. 

wiss.  Zool.,  bd.  15,  pp.  55-75,  I  taf. 
Plateau,  F.     1865,  1866.     Sur  la  force  musculaire  des  insectes.     Bull.  Acad. 

roy.   Belgique,  ser.  2,  t.  20,  pp.  732-757;  t.  22,  pp.  283-308. 
Merkel,  F.     1872,  1873.     Der  quergestreifte  Muskel.     Archiv  mikr.  Anat., 

bd.  8,  pp.  244-268,  2  taf. ;  bd.  9,  pp.  293-307. 
Lubbock,  J.     1877.     On   some   Points   in   the   Anatomy   of  Ants.     Month. 

Micr.  Journ.,  vol.  18,  pp.  121-142,  pis.  189-192. 
Lubbock,  J.     1879.     On  the  Anatomy  of  Ants.     Trans.   Linn.   Soc.   Zool., 

ser.  2,  vol.  2,  pp.  141-154,  2  pis. 


424  ENTOMOLOGY 

Poletajeff,  N.  1879.  Du  developpement  des  muscles  d'ailes  chez  les  Odo- 
nates.     Horse  Soc.  Ent.  Ross.,  t.  16,  pp.-  10-37,  5  pls- 

Von  Lendenfeld,  R.  1881.  Der  Flug  der  Libellen.  Ein  Beitrag  zur  Anat- 
omic vmd  Physiologie  der  Flugorgane  der  Insecten.  Sitzb.  Akad. 
Wiss.  Wien,  bd.  83,  pp.  289-376,  taf.   1-7. 

Luks,  C.  1883.  Ueber  die  Brustmuskulatur  der  Insecten.  Jenais.  Zeits. 
Naturw.,  bd.  16,  pp.  529-552,  taf.  22,  23. 

Dahl,  F.  1884.  Beitrage  zur  Kenntnis  des  Baues  und  der  Funktionen  der 
Insektenbeine.  Archiv  Naturg.,  jhg.  50,  bd.  i,  pp.  146-193,  taf. 
II-I3- 

Van  Gehuchten,  A.  1886.  fitude  sur  la  structure  intime  de  la  cellule  mus- 
culaire  striee.     La  Cellule,  t.  2,  pp.  289-453,  pls.  1-6. 

Miall,  L.  C,  and  Denny,  A.  1886.  The  Structure  and  Life-history  of  the 
Cockroach.     London  and  Leeds.*     (See  pp.  71-84.) 

Kblliker,  A.  1888.  Zur  Kenntnis  der  quergestreiften  Muskelfasern. 
Zeits.  wiss.  Zool.,  bd.  47,  pp.  689-710,  taf.  44,  45. 

Biitschli,  0.,  und  Schewiakoff,  W.  1891.  Ueber  den  feineren  Ban  der 
quergestreiften  Muskeln  von  Arthropoden.  Biol.  Centralb.,  bd. 
II,  PP-  33-39,  figs.  1-7- 

Rollet,  A.  1891.  Ueber  die  Streifen  N  (Nebenscheiben),  das  Sarko- 
plasma  und  Contraktion  der  quergestreiften  Muskelfasern.  Ar- 
chiv mikr.  Anat.,  bd.  ZT,  pp.  654-684,  taf.  zi- 

Janet,  C.  1895.  fitudes  sur  les  Fourmis,  les  Guepes  et  les  Abeilles. 
Note  12.  Structure  des  Membranes  articulaires  des  Tendons  et 
des  Muscles  (Myrmica,  Camponotus,  Vespa,  Apis).  26  pp.,  w 
figs.     Limoges. 

Janet,  C.  1895.  Sur  les  Muscles  des  Fourmis,  des  Guepes  et  des  Abeilles. 
Compt.  rend.  Acad.  Sc,  t.  121,  pp.  610-613,  i  fig. 


NERVOUS    SYSTEM 

Newport,  G.  1832,  1834.  On  the  Nervous  System  of  the  Sphinx  Ligustri 
Linn.,  and  on  the  changes  which  it  undergoes  during  a  part  of  the 
Metamorphoses  of  the  Insect.  Phil.  Trans.  Roy.  Soc.  London, 
vol.  122,  pp.  383-398,  2  pis.*  Part  II.  Phil.  Trans..  Roy.  Soc. 
London,  vol.  124,  pp.  389-423,  5  pis. 

Blanchard,  E.  1846.  Recherches  anatomiques  et  zoologiques  sur  le  sys- 
teme  nerveux  des  animaux  sans  vertebres.  Du  systeme  nerveux 
des  insectes.     Ann.  Sc.  nat.  Zool.,  ser.  3,  t.  5,  pp.  273-379,  8  pis. 

Leydig,  F.  1857.  Lehrbuch  der  Histologic  des  Menschen  und  der  Thicre. 
12 -|- 551   pp.,   figs.     Frankfurt. 

Leydig,  F.     1864.    Vom  Bau  des  Ticrischeii  Korpers.     Tubingen. 

Brandt,  E.  1876.  Recherches  anatomiques  et  morphologiques  sur  le  sys- 
teme nerveux  des  Insectes  Hymenoptercs.  Compt.  rend.  Acad. 
Sc,  t.  83,  pp.  613-616. 

Dietl,  M.  J.  1876.  Die  Organisation  des  Arthropodengehirns.  Zeits. 
wiss.  Zool,  bd.  27,  pp.  488-517,  taf.  36-38. 


LITERATURE  4-5 

Flogel,  J.  H.  L.     1878.     Ucbcr  den  einlicitlichen  Bau   des   Gfliirns   in   den 

verschiedenen    Insecten-Ordnungcn.      Zeits.    wiss.    Zool.,    bd.    30, 

SuppL,  pp.  556-592,  taf.  23,  24. 
Brandt,    E.     1879.     [Many    articles    on    the   nervous    system.]      IIor?e    Soc. 

Ent.  Ross.,  hd.  14-15.  taf.* 
Newton,  E.  T.     1879.     On  the   Brain  of  the   Cockroach,   Blatta  orientaHs. 

Quart.  Journ.  Micr.   Soc,  n.  s.,  vol.   19,  pp.  340-356,  pis.   15,   16. 
Michels,  H.     1880.     Beschrcibung  des  Nervensystems  von  Oryctes  nasicor- 

nis   im  Larven-,   Puppen-   und  Kaferzustandc.     Zeits.   wiss.   Zool, 

bd.  34,  pp.  641-702,  taf.  33-36. 
Packard,  A.  S.     1880.     The  Brain  of  the  Locust.     Second  Rcpt.  U.  S.  Ent. 

Comm..  pp.  223-242,  pis.  9-15,  fig.  9.     Washington.* 
Cattie,  J.  T.     1881.     Beitriige  zur  Kenntnis  der  Chorda  supra-spinalis  der 
.  Lepidoptera  und  des  ccntralen,  peripherischen  und  sympathischen 

Nervensystems   der  Raupen.     Zeits.   wiss.    Zool.,   bd.   35,   pp.   304- 

320,  taf.  16. 
Koestler,   M.     1883.     Ueber   das    Eingeweidenervensystem   von    Periplaneta 

oricntalis.     Zeits.  wiss.  Zool.,  bd.  39,  pp.  572-595,  taf.  34. 
Viallanes,    H.     1884-87.     fitudes    histologiques    et    organologiques    sur    les 

centres   nerveux   et   les   organes   des   sens   des   animaux   articules. 

^lem.    1-5.     Ann.   Sc.   nat.   Zool.,   ser.   6,  t.    17-19;   sen   7,  t.  2,  4; 

22  pis. 

Leydig,  F.     1885.     Zelle  und  Gewebe.     Nene  Beitrage  zur  Histologie  des 

Tierkorpers.     219  pp.,  6  taf.     Bonn. 
Viallanes,  H.     1887.     Sur  la  morphologic  comparee  du  cerveau  des  Insectes 

et  des  Crustaces.     Compt.  rend.  Acad.  Sc,  t.  104,  pp.  444-447. 
Binet,  A.     1894.     Contribution  a  I'etude  du  system  nerveux  sous-intestinal 

des   insectes.      Journ.   Anat.   Phys,,  t.  30,  pp.  449-580,  pis.   12-15, 

23  figs. 

Pawlovi,  M.  I.  1895.  On  the  Structure  of  the  Blood-Vessels  and  Sympa- 
thetic Nervous  System  of  Insects,  particularly  Orthoptera.  Works 
Lab.  Zool.  Cab.  Imp.  Univ.  Warsaw,  pp.  96  -|-  22,  tab.  1-6.  In 
Russian. 

Holmgren,  E.  1896.  Zur  Kenntnis  des  Hauptnervensystems  der  Arthro- 
poden.     Anat.  Anz.,  bd.  12,  pp.  449-457,  7  figs. 

Kenyon,  F.  C.  1896.  The  Brain  of  the  Bee.  Journ.  Comp.  Neurol.,  vol. 
6.  pp.  133-210,  pis.  14-22. 

Kenyon,  F.  C.  1896.  The  meaning  and  structure  of  the  so-called  "mush- 
room bodies  "  of  the  hexapod  brain.  Amer.  Nat.,  vol.  30,  pp.  643- 
650,  I  ^g. 

Kenyon,  F.  C.  1897.  The  optic  lobes  of  the  bee's  brain  in  the  light  of 
recent  neurological  methods.  Amer.  Nat.,  vol.  31,  pp.  369-376, 
pi.  9- 

SENSE    ORGANS;    SOUNDS 

Miiller,  J.  1826.  Zur  vergleichenden  Physiologie  des  Gesichtsinnes  der 
Menschen  und  der  Tiere.     462  pp.,  8  taf.     Leipzig. 


426  ENTOMOLOGY 

Von   Siebold,   C.   T.   E.     1844.     Ueber   das   Stimm-   und    Gehor-Organ   der 

Orthopteren.     Archiv  Naturg.  jhg.   10,  pp.  52-81,  fig. 
Gottsche,  C.  M.     1852.     Beitrag  zur  Anatomic  und  Phj'siologie  des  Anges 

der  Krebse  und   Fliegen.     Miiller's  Archiv  Anat.   Phys.,  pp.  483- 

492. 
Claparede,  E.     1859.     Zur  jMorphologie  der  zusammengesetzten  Augen  bei 

den  Arthropoden.     Zeits.  wiss.  ZooL,  bd.  10,  pp.  191-214,  3  taf. 
Hensen,  V.     1866.     Ueber  das  Gehororgan  von  Locusta.     Zeits.  wiss.  Zool., 

bd.  16,  pp.  190-207,  I  taf. 
Landois,    H.      1868.      Das    Gehororgan    des    Hirschkafers.      Archiv    mikr. 

Anat.,  bd.  4,  pp.  88-95. 
Schultze,  M.     1868.     Untersuchungen  iiber  die  zusammengesetzten  Augen 

der  Krebse  und   Insekten.     8  +  32   pp.,    12  taf.     Bonn. 
Scudder,  S.  H.     1868.     The  Songs  of  the  Grasshoppers.     Amer.  Nat.,  vol. 

2,  pp.  1 13-120,  5  figs. 
Scudder,  S.  H.     1868.     Notes  on  the  Stridulation  of  Grasshoppers.     Proc. 

Bost.  Soc.  Nat.  Hist.,  vol.  11,  pp.  306-313. 
Graber,   V.     1872.     Bemerkungen   iiber   die   Gehor-   und   Stimmorgane   der 

Heuschrecken    und    Cicaden.      Sitzb.    Akad.    Wiss.    Wien,    math.- 

naturw.   CI.,  bd.  66,   pp.   205-213,  2  figs. 
Paasch,  A.     1873.     Von  den  Sinnesorganen  der  Insekten  im  Allgemeinen, 

von  Gehor-  und  Geruchsorganen  im  Besondern.     Archiv  Naturg., 

jhg.  39,  bd.  I,  pp.  248-275. 
Forel,  A.     1874.     Les  fourmis  de  la  Suisse.     Neue  Denks.  allg.   Schweiz. 

Gesell.    Naturw.,   bd.   26,   480  pp.,   2   taf.     Separate,    1874,   4  +  457 

pp.,  2  taf.     Geneve. 
Mayer,  A.  M.     1874.     Experiments  on  the  supposed  Auditory  Apparatus 

of  the  Mosquito.     Amer.  Nat.,  vol.  8,  pp.  577-592,  fig.  92. 
Ranke,  J.     1875.     Beitrage   zu   der  Lehre  von   den  Uebergangs-Sinnesor- 

ganen.      Das    Gehororgan    der    Acridier    und    das    Sehorgan    der 

Hirudineen.     Zeits.  wiss.  ZooL,  bd.  25,  pp.   143-164,  taf.   10. 
Schmidt,  0.      1875.      Die  Gehororgane  der  Heuschrecken.      Archiv  mikr. 

Anat.,  bd.  11,  pp.  195-215,  taf.  10-12. 
Graber,    V.       1876.      Die    tympanalen    Sinnesapparate    der    Orthopteren. 

Denks.  Akad.  Wiss.  Wien,  bd.  36,  pp.  1-140,  10  taf. 
Graber,    V.      1876.      Die    abdominalen    Tympanalorgane    der    Cicaden    und 

Gryllodeen.     Denks.  Akad.  Wiss.  Wien,  bd.  36,  pp.  273-296,  2  taf. 
Mayer,   P.     1877.     Der   Tonapparat    der    Cikaden.     Zeits.    wiss.    Zool.,   bd. 

28,  pp.  79-92,  3  figs. 
Forel,  A.     1878.     Beitrag  zur  Kenntniss   der   Sinnesempfindungen   der   In- 
sekten.    Mitth.   Miinch.  ent.  Vereins,  jhg.   2,  pp.   1-21. 
Lowne,  B.  T.     1878.     On  the  Modifications  of  the  Simple  and  Compound 

Eyes   of   Insects.     Phil.   Trans.   Ro}-.    Soc.    London,   vol.    169,  pp. 

577-602,  pis.  52-54. 
Graber,  V.     1879.     Ueber  neue,  otocystenartige  Sinnesorgane  der  Insekten. 

Archiv  mikr.  Anat.,  bd.   16,  pp.  35-37,  2  taf. 


LITERATURE  427 

Grenacher,   H.      1879.      Untersuchungen    iiber   das    Sehorgan    der   Arthro- 

poden,  insbesondere  der  Spinnen,  Insckten  und  Crustaceen.     8  + 

188  pp.,  II  laf.     Gottingen. 
Hauser,  G.     1880.     Physiologische  und  histiologische  Untersuchungen  uber 

das   Geruchsorgan   der   Insekten.      Zeits.   wiss.   Zool,  bd.   34,   pp. 

367-403,  taf.  17-19. 
Graber,   V.      1882.      Die   chordotonalen   Sinnesorgane   und   das   Gehor   der 

Insecten.     Archiv   mikr.   Anat.,   bd.   20,  pp.   506-640,   taf.   30-35,   6 

figs.;  bd.  21,  pp.  65-145.  4  figs.* 
Lubbock,  J.     1882.     Ants,  Bees  and  Wasps.     19 -f- 448  pp.,  5  pis.,  31  figs. 

London.     1884,  1901,  New  York.     D.  Appleton  &  Co. 
Graber,  V.      1883.      Fundamentalversuche  iiber  die  Helligkeits-  und  Far- 

bencmpfindlichkeit     augenloser     und     geblendeter     Tiere.      Sitzb. 

Akad.  Wiss.  Wien,  bd.  87,  pp.  201-236. 
Carriere,  J.      1884.      On   the   Eyes  of   some   Invertebrata.      Quart.   Journ. 

Micr.  Sc,  vol.  24  (n.  s.),  pp.  673-681,  pi.  45. 
Graber,  V.     1884.     Grundlinien  zur  Erforschung  des  Helligkeits  und  Far- 

bensinnes  der  Tiere.     8  -J-  s^2  pp.     Prag  und  Leipzig. 
Lee,  A.  B.     1884.     Bemerkungen  iiber  den  feineren  Bau  der  Chordotonal- 

Organe.     Archiv  mikr.  Anat.,  bd.  23,  pp.  133-140,  taf.  7b. 
Lowne,  B.  T.     1884.     On  the  Compound  Vision  and  the  Morphology  of  the 

Eye  in  Insects.     Trans.  Linn.   Soc.   Zool,  vol.  2,  pp.  389-420,  pis. 

40-43- 
Carriere,  J.      1885.      Die   Sehorgane  der  Thiere,  vergleichend  anatomisch 

dargestellt.     6  -\-  205  pp.,   I   taf.,   147  figs.     Miinchen  und  Leipzig. 

R.  Oldenbourg. 
Hickson,  S.  J.     1885.    The  Eye  and  Optic  Tract  of  Insects.     Quart.  Journ. 

INIicr.  Sc,  vol.  25,  pp.  215-251,  pis.  15-17- 
Plateau,  F.     1885.     Experiences  sur  le   role  des  palpes  chez   les  Arthro- 

podes   maxilles.     Palpes   des    Insectes   broyeurs.     Bull.    Soc.    zool. 

France,  t.  10,  pp.  67-90. 
Plateau,   F,     1885-88.     Recherches  .experimentales   sur  la  vision  chez   les 

Insectes.     Bull.  Acad.  roy.  Belgique,  ser.  3,  t.  10,  14,  15,  16.     Mem. 

Acad.  roy.  Belgique,  t.  43,  pp.   1-91. 
Will,  F.      1885.      Das  Geschmacksorgan  der  Insekten.     Zeits.   wiss.   Zool., 

bd.  42,  pp.  674-707,  taf.  27. 
Forel,  A.     1886-87.     Experiences  et  remarques  critiques  sur  les  sensations 

des  Insectes.     Rec.  zool.  Suisse,  t.  4,  pp.  1-50,  145-240,  pi.  i. 
Graber,  V.     1887.     Neue  Versuche  iiber  die  Funktion  der   Insektenfiihler. 

Biol.  Centralb.,  bd.  7,  pp.  13-19. 
Mark,  E.  L.     1887.     Simple  Eyes  in  Arthropods.     Bull.  Mus.  Conip.  Zool., 

vol.   13,  pp.  49-105,  pis.  1-5- 
Patten,  W.      1887.      Eyes   of  Molluscs   and   Arthropods.     Journ.    Morph., 

vol.  I,  pp.  67-92,  pi.  3. 
Will,  F.     1887.     A.  Forel.     Sur  les  Sensations  des  Insectes.     Ent.  Nachr., 

jhg.  13,  pp.  227-233. 


428  ENTOMOLOGY 

Patten,  W.     1887,  1888.     Studies  on  the  Eyes  of  Arthropods.     I.  Develop- 
ment of  the   Eyes  of  Vespa,  with   Ohservations  on  the   Ocelli  of 

some  Insects.     Journ.  Morph.,  vol.   i,  pp.   193-226,  i  pi.     II.  Eyes 

of  Acilius.     Journ.  Morph..  vol.  2,  pp.  97-190,  pis.  7-13. 
Lubbock,   J.      1888,    1902.      On   the    Senses,    Instincts    and    Intelligence   of 

Animals,    with    Special    Reference    to    Insects.     29 -|- 292   pp.,    118 

figs.     New  York.     D.  Appleton  &  Co. 
Vom   Rath,    0.     1888.     Ueher   die    Hautsinnesorgane    der    Insekten.     Zeits. 

wiss.  Zool,  bd.  46,  pp.  413-454-  taf.  30,  31. 
Ruland,  F.     1888.     Beitriige  zur  Kenntnis  der  antennalen  Sinnesorgane  der 

Insekten.     Zeits.   wiss.   Zool.,  bd.   46,  pp.  602-628,  taf.  21- 
Lowne,  B.  T.     1889.     On  the  Structure  of  the  Retina  of  the  Blowfly  (Cal- 

liphora  erythrocephala).     Journ.  Linn.  Soc.  Zool.,  vol.  20,  pp.  406- 

417,  pi.  27. 
Packard,  A.  S.     1889.     Notes  on  the   Epipharynx,   and  the   Epipharyngeal 

Organs  of  Taste  in  ]\Iandibulate  Insects.     Psyche,  vol.  5,  pp.  193- 

199,  222-228. 
Pankrath,    0.      1890.      Das    Auge    der    Raupen    und    Phryganidenlarven. 

Zeits.  wiss.  Zool,  bd.  49,  pp.  690-708,  taf.  34,  35. 
Stefanowska,  M.     1890.     La  disposition  histologique  du  pigment  dans  les 

yeux  des  Arthropodes  sous  I'influence  de  la  lumiere  directe  et  de 

I'obscurite  complete.     Rec.  zool.  Suisse,  t.  5,  pp.   151-200,  pis.  8,  9. 
Watase,  S.     1890.     On  the  Morphology  of  the  Compound  Eyes  of  Arthro- 
pods.    Studies  Biol.  Lab.  Johns  Hopk.  Univ.,  vol.  4,  pp.  287-334, 

pis.  29-35. 
Weinland,    E,      1890.      Ueber    die    Schwinger    (Halteren)     der    Dipteren. 

Zeits.  wiss.  Zool,  bd.  51,  pp.  55-166,  taf.  7-11. 
,  Exner,  S.      1891.      Die   Physiologie  der  fazettierten   Augen  von   Krebsen 

und  Insekten.     8  +  206  pp.,  8  taf.,  23  figs.     Leipzig  und  Wien. 
Von  Adelung,  N.     1892.     Beitrage  zur  Kenntnis  des  tibialen  Gehorapparates 

der  Locustiden.     Zeits.  wiss.  Zool.,  bd.  54,  pp.  316-349,  taf.  14,  15. 
Nagel,    W.      1892.      Die    niederen    Sinne    der    Insekten.      68   pp.,    19    figs. 

Tubingen. 
Child,  C.  M.     1894.     Ein  bisher  wenig  beachtetes   antennales   Sinnesorgan 

der  Insekten,  mit  besonderer  Beriicksichtigung  der  Culiciden  und 

Chironomiden.     Zeits.  wiss.  Zool,  bd.  58,  pp.  475-528,  taf.  30,  31. 
Mallock,  A.     1894.     Insect   Sight   and   the   Defining   Power  of   Composite 

Eyes.     Proc.  Roy.  Soc.  London,  vol.  55,  pp.  85-90,  figs.  1-3. 
Vom  Rath,   0.     1896,     Zur  Kenntnis   der   Hautsinnesorgane   und   des   sen- 

siblen  Nervensystems  der  Arthropoden.     Zeits.  wiss.  Zool.,  bd.  61, 

PP-  499-539,  taf.  23,  24. 
Redikorzew,  W.      1900.      Untersuchungen  iiber  den  Bau  der  Ocellen  der 

Insekten.     Zeits.  wiss.  Zool.,  bd.  68,  pp.  581-624,  taf.  39,  40,  figs. 

1-7- 
Reuter,  E.     1896.     Ueber  die  Palpen  der  Rhopaloceren,  etc.     Acta  Soc.  Sc. 

Fenn.,  t.  22,  pp.   16  +  578,  6  tab. 


LITERATURE  4-9 

Hesse,  R.  igoi.  Untersuchungen  iiber  die  Organe  dei"  Lichtcmpfindung 
bei  niederen  Thieren.  VII.  Von  den  Arthropoden-Augen.  Zeits. 
wiss.  Zool.,  bd.  70,  pp.  347-473,  taf.  16-21,  figs,  i,  2. 

Schenk,  0.  1903.  Die  antennalen  Hautsinnesorgane  einiger  Lepidopteren 
iind  Hymenopteren  mit  besonderer  Beriicksichtigimg  der  sexuellen 
Unterschiede.  Zool.  Jalirb.,  Al)th.  Anat.  Ont.,  bd.  17,  pp.  573-6i8. 
taf.  21,  22,  4  figs.* 

DIGESTIVE    SYSTEM 

Dufour,  L.     1824-60.     [Many  important  papers.]     Am.   Sc.  nat.  Zool. 
Basch,  S.     1858.     Untcrsucbungen  iiber  das  cbylopoetiscbc  tmd  uropoctiscbe 

System   der   Blatta  orientalis.     Sitzb.    Akad.   Wiss.   Wien,   math.- 

naturw.  CI.,  bd.  33,  pp.  234-260,  5  taf. 
Sirodot,  S.     1858.     Rechercbes  sur  les  secretions  cbez  les  Insectes.     Ann. 

Sc.  nat.  Zool.,  ser.  4,  t.   10,  pp.   141-189,  251-334,   12  pis. 
Leydig,    F.     1859.     Zur    Anatomie    der    Insecten.     Midler's    Arcbiv    Anat. 

Pbys.,  pp.  33-89,  149-183,  3  taf. 
Fabre,  J.  L.     1862.     6tude  sur  le  role  du  tissu  adipeux  dans  la  secretion 

urinaire  cbez   les  Insectes.     Ann.   Sc.   nat.   Zool.,   ser.  4,  t.   19,  pp. 

351-382. 
Plateau,  F.     1874.     Recbcrcbes   sur  les  pbenomenes   de   la   digestion   cbez 

les  Insectes.     Mem.  Acad.  roy.  Belgique,  t.  41,  124  pp.,  3  pis. 
De  Bellesme,  J.     1876.     Physiologie  comparee.    Rechercbes  experimentales 

sur  la  digestion  des  insectes  et  en  particulier  de  la  blatte.     7  -j- 
,  96  pp..  3  pis.     Paris. 
Helm,  F.  E.     1876.     Ueber  die  Spinndriisen  der  Lepidopteren.     Zeits.  wiss. 

Zool.,  bd.  26,  pp.  434-469,  taf.  27,  28. 
Plateau,  F.     1877.     Note  additionelle  au  Memoire  sur  les  pbenomenes  de 

la  digestion  cbez  les   Insectes.     Bull.   Acad.   roy.   Belgique,  ser.  2, 

t.  44,  pp.  710-733- 
Wilde,  K.  F.      1877.      Untersuchungen  iiber  den  Kaumagen  der  Orthop- 

teren.     Arcbiv  Naturg.,  jhg.  43,  bd.  i,  pp.  135-172,  3  taf. 
De  Bellesme,  J.     1878.     Travaux  originaux   de  Physiologie  comparee.     I. 

Insectes.     Digestion,  Metamorphoses.     252  pp.,  5  pis.     Paris. 
Schindler,  E.     1878.     Beitrage  zur  Kenntniss  der  Malpighi'schen  Gefasse 

der  Insecten.     Zeits.  wiss.  Zool.,  bd.  30,  pp.  587-660,  taf.  38-40. 
Krukenberg,    C.   F,   W.     1880.     Versuche    zur   vergleichenden    Physiologie 

der   Verdauung    und    vergleichende    physiologische    Beitrage    zur 

Kenntnis    der    Verdauungsvorgange.      Unters.    pbys.    Inst.    Univ. 

Heidelberg. 
Frenzel,  J.     1882.     Ueber  Bau  und  Tbatigkeit  des  Verdauungskanals   der 

Larve  des  Tenebrio  molitor  mit  Beriicksichtigung  anderer  Artbro- 

poden.     Berl.  ent.  Zeits.,  bd.  26,  pp.  267-316,  taf.  5.* 
Leydig,    F.      1883.      Untersuchungen    zur    Anatomie    und    Histologic    der 

Tbiere.     174  pp.,  8  taf.     Bonn. 


430  ENTOMOLOGY 

Metschnikoff,   E.     1883.     Untersuchungen   iiber   die   intrazellulare   Verdau- 

ung  bei  wirbellosen  Tieren.     Arb.  zool.  Inst.  Wien,  bd.  5,  pp.  141- 
168.  2  taf. 
Schiemenz,    P.     1883.     Ueber    das    Herkommen    des    Futtersaftes    und    die 

Speicheldriisen  der  Biene  nebst  einem   Anhange  iiber  das  Riech- 

organ.     Zeits.  wiss.  Zool,  bd.  38,  pp.  71-135,  taf.  5-7. 
Locy,    W.    A.     1884.     Anatomy    and    Physiology    of    the    family    Nepidse. 

Amer.  Nat.,  vol.  18,  pp.  250-255,  353-367,  pls.  9-12. 
Witlaczil,  E.     1885.     Zur  Morphologic  und  Anatomie  der  Cocciden.     Zeits. 

wiss.  Zool.  bd.  43,  pp.  149-174,  taf.  5. 
Frenzel,  J.     1886.     Einiges  iiber  den  Mitteldarm  der  Insekten,  sowie  iiber 

Epithelregeneration.     Archiv  mikr.  Anat.,  bd.  26,  pp.  229-306,  taf. 

7^- 
Kniippel,  A.     1886.     Ueber  Speicheldriisen  von  Insecten.     Archiv  Natnrg., 

jhg.  52,  bd.  I,  pp.  269-303,  taf.   13,  14. 
Cholodkovsky,    N.     1887.     Sur   la    morphologic    dc   I'apparcil    urinairc    des 

Lepidoptercs.     Archiv.  Biol.,  t.  6,  pp.  497-514,  pi.   17. 
Faussek,  V.     1887.     Beitrage  zur  Histologic  des  Darmkanals  der  Insekten. 

Zeits.  wiss.  Zool.,  bd.  45,  pp.  694-712,  taf.  36. 
Kowalevsky,  A.     1887.     Beitrage  zur  Kenntnis  der  nachcmbryonalen  Ent- 

wicklung  der  IMusciden.     Zeits.   wiss.    Zool.,   bd.   45,   pp.   542-594, 

taf.  26-30. 
Schneider,  A.     1887.     Ueber  den  Darmcanal  der  Arthropoden.     Zool.  Beitr. 

von  A.  Schneider,  bd.  2,  pp.  82-96,  taf.  &-10. 
Emery,    C.     1888.     Ueber   den    sogenannten    Kaumagen    einiger    Ameisen. 

Zeits.  wiss.  Zool.,  bd.  46,  pp.  378-412,  taf.  27-29. 
Macloskie,    G.      1888.      The    Poison    Apparatus    of   the    Mosquito.      Amer. 

Nat.,  vol.  22,  pp.  884-888,  2  figs. 
Blanc,  L.     1889.     fitude  sur  la  secretion  de  la  sole  et  sur  la  structure  du 

brin  et  dc  la  have  dans  le  Bombj^x  mori.     56  pp.,  4  pis.     Lyon. 
Kowalevsky,  A.     1889.     Ein  Beitrag  zur  Kenntnis  der  Exkretionsorgane. 

Biol.  Centralb.,  bd.  9,  pp.  33-47,  65-76,  127-128. 
Van  Gehuchten,  A.     1890.     Recherches  histologiques  sur  I'apparcil  digestif 

dc    la   larve   dc    la    Ptychoptcra    contaminata.    I    Part,     fitude    du 

revetement  epithelial  ct  recherches  sur  la   secretion.     La   Cellule, 

t.  6,  pp.  183-291,  pis.  1-6. 
Gilson,   G.     1890,   1893.     Recherches   sur  Ics  cellules  secretantes.     La   soie 

et    les    appareils    sericigenes.      I.  Lepidoptercs;     II.  Trichopteres. 

La  Cellule,  t.  6,  pp.  1 15-182,  pis.  1-3;  t.   10,  pp.  37-63,  pi.  4. 
Blanc,  L.     1891.     La  tetc  du  Bombyx  mori  a  I'etat  larvaire,   anatomie  et 

physiologic.     Trav.    Lab.    fitud.    Soie,    1889-1890,    180  pp.,   95   figs. 

Lyon. 
Wheeler,   W.   M.     1893.     The  primitive   number   of   Malpighian   vessels   in 

Insects.      Psyche,   vol.    6,   pp.   457-460,   485-486,   497-498,   509-510, 

539-541,  545-547,  561-564. 


LITERATURE  43  ^ 

Bordas,    L.      1895.      Apparcil    glandulaire    dcs    Hymenopteres.      (Glandes 

salivaircs,  tul)e  discstif,  tubes  de  JNIalpislii  et  glandes  venimeuses.) 

362  pp.,   1 1   pis.     Paris. 
Cuenot,    L.      1895.      fitndes    physiologiques    sur    les    Orthopteres.      Arch. 

Biol.  t.   14.  pp.  293-341,  pis.  12,  13. 
Bordas,  L.     1897.     L'appareil  digestif  des  Orthopteres.     Ann.  Sc.  nat.  ZooL. 

ser.  8,  t.  5,  pp.   1-208,  pis.   1-12. 
Needham,   J.   G.     1897.     The    digestive   epithelium   of   dragon    fly   nymphs. 

Zo(5l.  P.ull.,  vol.  T,  pp.  103-113,  figs.  i-io. 

CIRCULATORY    SYSTEAI 
Newport,  G.     1839.     Insecta.     Todd's  Cyclopaedia  Anat.   Phys.,  vol.  2,  pp. 

853^94.  figs.  329-439- 
Newport,  G.      1845.     On  the    Structure   and   Development   of  the   Blood. 

Ann.  Mag.  Nat.  Hist.,  vol.   15,  pp.  281-284. 
Verloren,    M.    C.     1847.     [Memoire    sur    la    circulation    dans    les    insectes.] 

jNIem.  Acad.  roy.  Belgique,  t.   19,  93  pp.,  7  pis. 
Blanchard,  E.     1848.     De  la  circulation  dans  les   insectes.     Ann.   Sc.   nat. 

Zool.,  ser.  3,  t.  9,  pp.  359-398,  5  pis. 
Ley  dig,  F.     1851.    Anatomisches  und  Histologisches  fiber  die  Larve  von 

Corethra  plumicornis.     Zeits.   wiss.   Zool,   bd.   3,  pp.   435-451,   taf. 

16. 
Scheiber,    S.    H.      i860.      Vergleichende    Anatomic    und    Physiologie    der 

CEstriden-Larven.     Sitzb.    Akad.    Wiss.    Wien,   math.-naturw.    CI., 

bd.  41,  pp.  409-496,  2  taf. 
Landois,   H.      1864.      Beobachtungen   fiber   das   Blut   der   Insekten.      Zeits. 

wiss.  Zool.,  bd.   14,  pp.  55-70-  3  taf. 
Graber,  V.     1871.     Ueber  die   Blutkorperchen  der   Insekten.     Sitzb.   Akad. 

Wiss.  Wien,  math.-naturw.  CI.,  bd.  64,  pp.  9-44- 
Moseley,  H.  N.     1871.     On  the  circulation  in  the  wings  of  Blatta  orientalis 

and  other  insects,   and  on  a  new  method  of  injecting  the  vessels 

of  insects.     Quart.   Journ.   Micr.   Sc,  vol.   11    (n.   s.),  pp.  389-395. 

I  pi. 
Graber,    V.     1873.     Ueber    den    propulsatorischen    Apparat    der    Insekten. 

Archiv  mikr.  Anat.,  bd.  9,  pp.   129-196,  3  taf. 
Graber,  V.     1873.     Ueber  die  Blutkorperchen  der  Insekten.     Sitzb.   Akad. 

Wiss.  Wien,  math.-naturw.  CI.,  bd.  64   (1871),  pp.  9-44. 
Graber,  V.     1876.     Ueber  den  pulsierenden  Bauchsinus  der  Insekten.     Ar- 
chiv mikr.  Anat.,  bd.  12,  pp.  575-582,  i  taf. 
Dogiel,  J.     1877.     Anatomic  und  Physiologie  des   Herzens   der  Larve  von 

Corethra  plumicornis.     Mem.  Acad.  St.  Petersbourg,  ser.  7,  t.  24, 

^i']  pp.,  2  pis.     Separate,  Leipzig.     Voss. 
Jaworovski,   A.      1879.      Ueber  die  Entwicklung  des  Riickengefasses  und 

speziell  der  Muskulatur  bei  Chironomus  und  einigen  anderen  In- 
sekten.    Sitzb.  Akad.  Wiss.  Wien,  math.-naturw.   CI,  bd.  80,  pp. 

238-258. 


432  ENTOMOLOGY 

Plateau,   F.      1879.      Communication  preliminaire   sur   les   mouvements   et 

I'innervation  de  I'organe  central  de  la  circulation  chez  les  animaux 

articules.     Bull.  Acad.  roy.  Belgique,  ser.  2.  t.  46,  pp.  203-212. 
Zimmermann,  0.     1880.     Ueber  eine  eigenthiimliche  Bildung  des  Riicken- 

gefasses  bei  einigen  Ephemeridenlarven.     Zeits.  wiss.  Zool.,  bd.  34, 

pp.  404-406,  figs.  1-4. 
Burgess,   E.      1881.      Note   on   the    aorta   in    lepidopterous    insects.      Proc. 

Bost.  Soc.  Nat.  Hist,  vol.  21.  pp.  153-156,  figs.  i-5- 
Vayssiere,  A.     1882.     Recherches  sur  I'organisation  des  larves  des  Ephe- 

merines.     Ann.  Sc.  nat.  Zool.,  ser.  6,  t.  13,  pp.  1-137,  pls.  i-ii. 
Viallanes,  H.     1882.     Recherches   sur  Thistologie  des  Insectes,  et  sur  les 

phenomenes    histologiques    qui    accompagnent    le    developpement 

post-embryonnaire  de  ccs  animaux.     Ann.  Sc.  nat.  Zool.,  ser.  6,  t. 

14,  pp.  1-348,  4  pis.     Bibl.  ficole,  bd.  26,  348  pp.,  18  pis. 
Creutzburg,  N.     1885.     Ueber  den   Kreislauf  der  Ephemerenlarven.     Zool. 

Anz.,  jhg.  8,  pp.  246-248. 
Poletajewa,  0.     1886.     Du  cceur  des  insectes.     Zool.  Anz.,  jhg.  9,  pp.  13-15. 
Von    Wielowiejski,    H.    R.      1886.      Ueber    das    Blutgewebe    der    Insekten. 

Zeits.  wiss.  Zool.,  bd.  43,  pp.  512-536. 
Dewitz,   H.      1889.      Eigenthatige   Schwimmbewegung   der   Blutkorperchen 

der  Gliederthiere.     Zool.  Anz.,  jhg.  12,  pp.  457-464,   i  fig. 
Kowalevsky,  A.     1889.     Ein   Beitrag  zur   Kenntnis   der  Excretionsorgane. 

Biol.  Centralb.,  bd.  9,  pp.  33-47,  65-76,  127-128. 
Schaffer,    C.      1889.      Beitrage    zur    Histologic    der    Insekten.      H.  Ueber 

Blutbildungsherde   bei   Insektenlarven.     Zool.   Jahrb.,   Abth.   Anat. 

Ont..  bd.  3.  pp.  626-636,  taf.  30. 
Lankester,  E.   R.      1893.      Note  on  the   Qulom   and   Vascular   System   of 

Mollusca  and  Arthropoda.     Quart.   Journ.    Micr.   Sc,   vol.   34    (n. 

s.),  pp.  427-432. 
Pawlowa,     M.      1895.      Ueber    ampullenartige     Blutcirculationsorgane     im 

Kopfe  verschiedener  Orthopteren.     Zool.   Anz.,   jhg.    18,  pp.   7-13, 

I   fig. 

FAT    BODY 

Dufour,  L.     1826.     Recherches  anatomiques  sur  les  Carabiques  et  sur  plu- 

sieurs    autres    Insectes    Coleopteres.     Du    tissu    adipeux    splanch- 

nique.     Ann.  Sc.  nat.  Zool.,  t.  8,  pp.  29-35. 
Meyer,  H.     1848.     Ueber  die  Entwicklung  des  Fettkorpers,  der  Tracheen 

und   der  keimbereitenden  Geschlechtstheile  bei   den   Lepidopteren. 

Zeits.  wiss.  Zool.,  bd.  i,  pp.  175-197,  4  taf. 
Fabre,  J.  H.     1863.     fitude  sur  le  role  du  tissu  adipeux  dans  la  secretion 

urinaire  chez   les   Insectes.     Ann.   Sc.   nat.   Zool.,   ser.  4,   t.   19,  pp. 

351-382. 
Landois,    L.      1865.      Ueber    die    Funktion    des    Fettkorpers.      Zeits.    wiss. 

Zool.,  bd.  15,  pp.  ?,7^-27^- 


LITERATURE  433 

Schultze,    M.      1865.      Zur    Kenntniss    der    Leuchtorgane    von    Lampyris 

splcndidnla.     Archiv  mikr.  Anat.,  bd.  i,  pp.   124-137,  taf.  5,  6. 
Gadeau  de  Kerville,  H.     1881,  1887.     Les  insectes  phosphorescents.     T.   i, 

55  pp.,  4  pis. ;  t.  2,  13s  pp.     Rouen.* 
Von   Wielowiejski,   H.   R.     1882.     Studien    iiber    Lampyriden.     Zcits.    wiss. 

Zool.,  bd.  Z7,  pp.  354-428,  taf.  23,  24. 
Von  Wielowiejski,  H.     1883.    Ueber  den  Fettkorper  von  Corcthra  plumi- 

cornis  und  seine  Entwicklimg.     Zool.  Anz.,  jhg.  6,  pp.  318-322. 
Emery,  C.      1884.     Untersuchungen  iiber  Luciola  italica  L.      Zeits.   wiss. 

Zool.,  bd.  40,  pp.  338-355.  taf.  19. 
Emery,  C.     1885.     La  luce  della  Luciola  italica  osservata  ron  microscopio. 

Bull.  Soc.  Ent.  Ital.,  anno  17,  pp.  351-355-  tav.  5. 
Dubois,  R.     1886.     Contribution  a  I'etude  de  la  production  de  la  lumiere 

par  les  etres  vivants.     Les  Elaterides  lumineux.     Bull.  Soc.  zool. 

France,  ann.  11,  pp.  1-275,  pls.   i-9- 
Heinemann,  C.     1886.     Zur  Anatomic  und   Physiologic   der  Leuchtorgane 

niexikanischer  Cucuyo's.     Archiv  niikr.  Anat.,  bd.  27,  pp.  296-382. 
Von    Wielowiejski,    H.    R.      1886.      Ueber    das    Blutgewebe    der    Insekten. 

Zeits.  wiss.  Zool.,  bd.  43,  pp.  512-536. 
Schaffer,    C.      1889.      Beitrage    zur    Histologic    der    Insekten.      H.    Ueber 

Blutbildungsherde   bei   Liscktenlarven.     Zool.   Jahrb.,   Abth.   Anat. 

Out.,  bd.  3,  pp.  626-636,  taf.  30. 
Von  Wielowiejski,  H.  R.     1889.     Beitrage  zur  Kenntnis  der  Leuchtorgane 

der  Insecten.     Zool.  Anz.,  jhg.  12,  pp.  594-600. 
Wheeler,  W.  M.      1892.      Concerning  the  "blood  tissue"  of  the   Insecta. 

Psyche,  vol.  6,  pp.  216-220,  233-236,  253-258,  pi.  7. 
Cuenot,  L.     1895.     fitudes  physiologiques  sur  les  Orthopteres.     Arch.  Biol, 

t.  14,  pp.  293-341,  pis.  12,  13. 
Schmidt,  P.     1895.     On  the  Luminosity  of  Midges   (Chironomidse).     Ann. 

IXLig.   Nat.  Hist.,  ser.  6,  vol.   15,  pp.   133-141.     Trans,  from  Zool. 

Jahrb.,  Abth.  Syst.,  etc.,  bd.  8,  pp.  58-66,  1894. 

RESPIRATORY    SYSTEM 

Dufour,  L.  1825-60.  [^lany  papers  on  respiratory  system.]  Ann.  Sc.  nat. 
Zool. 

Dutrochet,  R.  J.  H,  1833.  Du  mecanisme  de  la  respiration  des  Insectes. 
Ann.  Sc!  nat.  Zool.,  t.  28,  pp.  31-44.  1838.  Mem.  Acad.  Sc.  Paris, 
t.  14,  pp.  81^3. 

Newport,  G.  1836.  On  the  Respiration  of  Insects.  Phil.  Trans.  Roy.  Soc. 
London,  vol.  126,  pp.  529-566. 

Grube,  A.  E.  1844.  Beschreibung  einer  auffallendcn  an  Siisswasser- 
schwammen  lebenden  Larve.  (Sisyra.)  Archiv  Naturg.,  jhg.  9, 
pp.  331-337.  figs. 

Newport,  G.  1844.  On  the  existence  of  Branchiae  in  the  perfect  State  of 
a  Neuropterous  Insect,  Pteronarcys  regalis  Newm.  and  other  spe- 
cies of  the  same  genus.  Ann.  Mag.  Nat.  Hist.,  vol.  13,  pp.  21-25. 
29 


434  ENTOMOLOGY 

Platner,  E.  A.  1844.  ^littheilungen  iiber  die  Respirationsorgane  und  die 
Haut  der  Seidenraupen.  Miiller's  Archiv  Anat.  Phys.,  pp.  38-49, 
figs. 

Dufour,  L.  1849.  Des  divers  modes  de  respiration  aquatique  dans  les 
insectes.  Compt.  rend.  Acad.  Sc,  t.  29,  pp.  763-770.  1850.  Trans. 
Ann.  "Slag.  Nat.  Hist.,  sen  2,  vol.  6,  pp.   112-118. 

Newport,  G.  1851.  On  the  Formation  and  the  Use  of  the  Airsacs  and 
dilated  Tracheae  in  Insects.  Trans.  Linn.  Soc.  Zool,  vol.  20,  pp. 
419-423. 

Newport,  G.  1851.  On  the  Anatomy  and  Affinities  of  Pteronarcys  regalis 
Newm.,  etc.     Trans.  Linn.  Soc.  Zool,  vol.  20,  pp.  425-453,  i  pi. 

Dufour,  L.  1852.  fitudes  anatomiques  et  physiologiqnes  et  observations 
sur  les  larves  des  Libellules.  Ann.  Sc.  nat.  Zool.,  ser.  3,  t.  17,  pp. 
65-110,  3  pis. 

Hagen,  H.  A.  1853.  Leon  Dnfour  iiber  die  Larven  der  Libellen  mit 
Beriicksichtigung  der  friiheren  Arbeiten.  (Ueber  Respiration  der 
Insecten.)  Stett.  ent.  Zeit.,  bd.  14,  pp.  98-106,  237-238,  260-270, 
311-325,  334-346. 

Williams,  T,  1853-57.  Oi''  the  Mechanism  of  Aquatic  Respiration  and  on 
the  Structure  of  the  Organs  of  Breathing  in  Invertebrate  Ani- 
mals.    Trans.  Ann.  Mag.  Nat.  Hist.,  ser.  2,  vols.  12-19,  ^7  p's- 

Barlow,  W.  F.  1855.  Observations  of  the  Respiratory  Movements  of  In- 
sects.    Phil.  Trans.  Roy.  Soc.  London,  vol.  145,  pp.  139-148. 

Lubbock,  J.  i860.  On  the  Distribution  of  the  Tracheae  in  Insects.  Trans. 
Linn.  Soc.  Zool.,  vol.  23.  pp.  23-50,  pi.  4. 

Rathke,  H.  1861.  Anatomisch-physiologische  Untersuchungen  iiber  den 
Athmungsprocess  der  Insecten.  Schrift,  phys.-oek.  Gesell.  Kon- 
igsberg,  jhg.   i,  pp.  99-138,  taf.   i. 

Scheiber,  S.  H.  1862.  Vergleichende  Anatomic  und  Physiologic  der 
Q^striden-Larven.  Respirationssystem.  Sitzb.  Akad.  Wiss.  Wien, 
math.-naturw.  CI.,  bd.  45,  pp.  7-68,  3  taf. 

Reinhard,  H.  1865.  Zur  Entwicklungsgeschichte  des  Tracheensystems  der 
Hj-menopteren  mit  besonderer  Beziehung  auf  dessen  morpholo- 
gische  Bedeutung.     Berl.  cnt.  Zeits.,  jhg.  9,  pp.  187-218,  taf.  i,  2. 

Landois,  H.,  und  Thelen,  W.  1867.  Der  Tracheenverschluss  bei  den  In- 
sekten.     Zeits.  wiss.  Zool.,  bd.  17,  pp.  187-214,  i  taf. 

Oustalet,  E.  1869.  Note  sur  la  respiration  chez  les  nymphes  des  Libel- 
lules.    Ann.  Sc.  nat.  Zool.,  ser.  5,  t.   11,  pp.  370-386,  3  pis. 

Pouchet,  G.  1872.  Developpement  du  systeme  tracheen  de  I'Anophele 
(Corethra  plumicornis).  Archiv.  Zool.  exper.,  t.  i,  pp.  217-232, 
I  fig. 

Gerstacker,  A,  1874.  Ueber  das  Vorkommen  von  Tracheenkiemen  bei 
ausgebildeten  Insecten.  Zeits.  wiss.  Zool.,  bd.  24,  pp.  204-252,  i 
taf. 

Packard,  A.  S.  1874.  On  the  Distribution,  and  Primitive  Number  of 
Spiracles  in  Insects.     Amer.  Nat.,  vol.  8,  pp.  531-534- 


LITERATURE  435 

Palmen,  J.  A.      1877.      Zur  ^Morphologic  des  Tracheensystcms.      10 -f- 149 

pp.,  2  taf.     Helsingfors. 
Sharp,  D.     1877.     Observations  on  the  Respiratory  Action  of  the  Carnivo- 
rous Water  Beetles  (Dytiscidse).     Journ.  Linn.  Soc.  ZooL,  vol.  13, 

pp.   161-183. 
Haller,  G.     1878.     Kleinere  Bruchstiicke  zur  vergleichenden  Anatomic  der 

Artliropoden.      I.  Ueber    das    Atmungsorgan    der    Stechmiicken- 

larvcn.     Archiv  Natnrg.,  jhg.  44,  bd.  i,  pp.  91-101,  taf.  2. 
Hagen,  H.  A.     1880.     Beitrag  zur  Kenntnis  des  Tracheensystcms  der  Libel- 

len-Larven.     Zool.  Anz.,  jhg.  3,  pp.  157-161. 
Hagen,  H.  A.      1880.      Kiemenubcrreste  bei  einer  Libelle ;   glatte  Muskel- 

fascrn  bei  Insectcn.     Zool.  Anz.,  jhg.  3,  pp.  304-305- 
Poletajew,  0.     1880.     Quelques  mots  sur  les  organes  respiratoires  des  lar- 

ves  des  Odonates.     Horse  Soc.  Ent.  Ross.,  t.  15,  pp.  436-452,  2  pis. 
Viallanes,  H.     1880.     Sur  Tapparcil  respiratoire  et  circulatoire  de  quelques 

larvos  de  Dipteres.     Compt.  rend.  Acad.   Sc,  t.  90,  pp.   1180-1182. 
Krancher,  0.     1881.     Der  Ban  der  Stigmen  bei  den  Insekten.     Zeits.  wiss. 

Zool,  bd.  35,  pp.  505-574-  taf.  28,  29. 
Vayssiere,  A.     1882.    Recherches  sur  I'organisation  des  larves  des  Ephe- 

merines.     Ann.  Sc.  nat.  Zool.,  sen  6,  t.  13,  pp.  1-137,  pis.  i-ii. 
Macloskie,  G.     1883.     Pneumatic  Functions  of  Insects.     Psyche,  vol.  3,  pp. 

375-378. 
Macloskie,  G.      1884.      The  Structure  of  the  Trachese  of  Insects.     Amer. 

Nat.,  vol.   18,  pp.  567-573.  figs.   1-4. 
Plateau,  F.      1884.      Recherches   experimentales   sur  les   mouvements   res- 
piratoires des  Insectes.     Mem.  Acad.  roy.  Belgique,  t.  45,  219  pp., 

7  pis.,  56  figs. 
Packard,  A.  S.     1886.     On  the  Nature  and  Origin  of  the  so-called  "  Spiral 

Thread  "  of  Trachese.     Amer.  Nat.,  vol.  20,  pp.  438-442,  figs.  1-3. 
Comstock,  J.   H.      1887.      Note  on  Respiration  of  Aquatic  Bugs.      Amer. 

Nat.,  vol.  21,  pp.  577-578. 
Raschke,  E.  W.     1887.     Die  Larve  von  Culex  nemorosus.     Archiv  Naturg., 

jhg.  53.  bd.  I,  pp.  133-163.  taf.  5,  6. 
Schmidt-Schwedt,   E.      1887.      Ueber   Athmung   der   Larven    und    Puppen 

von    Donacia    crassipes.     Berlin,    ent.    Zeits.,   bd.    31,   pp.    325-334, 

taf.  5b. 
Vogler,     C.      1887.      Die     Tracheenkiemen     der     Simulien-Puppen.      Mitt. 

schweiz.  ent.  Gesell.,  bd.  7,  pp.  277-282. 
Dewitz,  H.     1888.     Entnehmen  die  Larven  der  Donacien  vermittclst  Stig- 
men oder  Athemrohren  den  Luftraumen  der  Pflanzen  die  sauer- 

stoffhaltige  Luft?     Bed.  ent.  Zeits.,  bd.  32,  pp.  5-6,  figs,  i,  2. 
Haase,  E.      1889.      Die  Abdominalanhange  der  Insekten  mit  Beriicksichti- 

gung  der   Myriopoden.      Morph.   Jahrb.,   bd.    15,   pp.   331-43S,   taf. 

14.  15- 
Cajal,  S.  R.     1890.     Coloration  par  la  methode  de  Golgi  des  terminaisons 

des  trachees  et  des  nerfs  dans  les  muscles  des  ailes  des  insectes. 

Zeits.  wiss.  Mikr.,  bd.  7,  pp.  332-342,  taf.  2,  figs.  1-3. 


43^  ENTOMOLOGY 

Dewitz,  H.  1890.  Einige  Beobachtungen,  betreffend  das  geschlossene 
Tracheensystem  bei  Insectenlarven.  Zool.  Anz.,  jhg.  13,  pp.  500- 
504,  525-531- 

Von  Wistinghausen,  C.  1890.  Ueber  Tracheenendigungen  in  den  Sericte- 
ricn  der  Raupen.     Zeits.  wiss.  Zool.,  bd.  49,  pp.  565-582,  taf.  27.* 

Miall,  L.  C.  1891.  Some  Difficulties  in  the  Life  of  Aquatic  Insects.  Na- 
ture, vol.  44,  pp.  457-462. 

Stokes,  A.  C.  1893.  The  Structure  of  Insect  Tracheae,  with  Special  Ref- 
erence to  those  of  Zaitha  fluminea.  Science,  vol.  21,  pp.  44-46, 
figs.   1-7. 

Miall,  L.  C.  1895,  1903.  The  Natural  History  of  Aquatic  Insects.  11  + 
395  PP-j  116  figs.     London  and  New  York.     Macmillan  &  Co. 

Sadones,  J.  1895.  L'appareil  digestif  et  respiratoire  larvaire  des  Odo- 
nates.     La  Cellule,  t.   11,  pp.  271-325,  pis.   1-3. 

Gilson,  G.,  and  Sadones,  J.  1896.  The  Larval  Gills  of  the  Odonata. 
Journ.  Linn.  Soc.  Zool.,  vol.  25.  pp.  413-418,  figs.   1-3. 

Holmgren,  E.  1896.  Ueber  das  respiratorische  Epithel  der  Tracheen  bei 
Raupen.     Festsk.  Lilljeborg,  Upsala,  pp.  79-96,  taf.  5,  6. 

REPRODUCTIVE   SYSTEM 

Dufour,   L.     1824-60.     [Many   papers   on   reproductive    system.]     Ann.    Sc. 

nat.  Zool. 
Dutrochet,  R.  J.  H.     1833.     Observations  sur  les  organes  de  la  generation 

chez  les  Pucerons.     Ann.  Sc.  nat.  Zool.,  t.  30,  pp.  204-209. 
Von  Siebold,  C.  T.  E.     1836.     Ueber  die  Spermatozoen  der  Crustaceen,  In- 

sccten,     Gasteropoden    und    einiger    andern    wirbellosen    Thiere. 

Miiller's  Archiv  Anat.  Phys.,  pp.  15-52,  2  taf. 
Von  Siebold,  C.  T.  E,     1836,     Fernerer  Beobachtungen  iiber  die  Spermato- 
zoen   der   wirbellosen   Thiere.      Miiller's    Archiv    Anat.    Phys.,   p. 

232.     1837,  pp.  381-432,  taf.  I. 
Doyere,  L.     1837.     Observations  anatomiques  sur  les  Organes  de  la  genera- 
tion chez  la  Cigale  femelle.     Ann.  Sc.  nat.  Zool.,  t.  7,  pp.  200-206, 

figs. 
Von  Siebold,  C.  T.  E.     1838.     Ueber  die  weiblichen  Geschlechtsorgane  der 

Tachinen.     Archiv  Naturg.,  jhg.  4,  pp.   191-201. 
Loew,    H.     1841.     Beitrag    zur    anatomischen    Kenntniss    der    inneren    Ge- 

schlechtstheile   der  zweifliigligen   Insecten.      Germar's   Zeits.   Ent., 

bd.  3,  pp.  386-406,  I  taf. 
Von  Siebold,  C.  T.  E.     1843.     Ueber   das   Receptaculum  seminis   der   Hy- 

menopteren   Weibchen.     Germar's   Zeits.   Ent.,   bd.   4,   pp.   362-388, 

I  taf. 
Stein,   F.     1847.     Vergleichende   Anatomic   und   Physiologie   der   Insecten. 

I.  Monographie.     Ueber  die  Geschlechts-Organe  und  den  Bau  des 

Hinterleibes    bei    den    weiblichen    Kafern.      8+139    pp.,    9    taf. 

Berlin. 


LITERATURE  437 

Brauer,   F.      1855.      Beitriige    zur   Kcnntniss    dcs    inncrcn    Raues   und    der 

V^erwandlung  der   Neuroptercn.     Verli.   zool.-bot.   Vor.    Wicn,  bd. 

5,  pp.  700-726,  5  taf. 
Kolliker,    A.      1856.      Physiologische    Studien    iiber    die    Sanicnniissigkeit. 

Zeits.  wiss.  Zool.,  bd.  7,  pp.  201-272,  i  taf. 
Huxley,  T.  H.     1858-59.     (^n  tbc  Agamic  Reproduction  and   Morpliology 

(if  Apliis.     Trans.  Linn.  Soc.  Zool.,  vol.  22,  pp.  193-236,  5  pis. 
Lubbock,  J.     1859.     On  tbe  Ova  and   Pseudova  of  Insects.     Pbil.  Trans. 

Roy.  Soc.  London,  vol.  149,  pp.  341-369,  pis.  16-18. 
Landois,  H.     1863.     Ucbcr  die  Verbindung  der  Hoden  niit  dem  Riickenge- 

fjiss  bei   den   Insekten.     Zeits.   wiss.   Zool.,   bd.    13,   pp.   316-318,   i 

taf. 
Claus,  C.     1864.     Beobachtungen  iibcr  die  Rildung  des  Insekteneies.     Zeits. 

wiss.  Zool.,  bd.   14,  pp.  42-54,   r   taf. 
Pagenstecher,   H.   A.     1864.     Die  ungescblccbtlicbe   Vermebnmg  der   Flie- 

genlarven.     Zeits.  wiss.  Zool,  bd.   14,  pp.  400-416,  2  taf. 
Wagner,    N.     1865.     Ueber    die    viviparen    Gallmiickenlarven.     Zeits.    wiss. 

Zool,  bd.  15,  pp.   106-117. 
Bessels,  C.     1867.     Studien  fiber  die  Entwicklung  der  Sexualdriisen  bei  den 

Lepidopteren.     Zeits.  wiss.  Zool,  bd.   17,  pp.  545-564,  3  taf. 
Leydig,    F.      1867.      Der    Eierstock    und    die    Samentascbe    der    Insekten. 

Nova  Acta  Acad.  Leop. -Carol.,  bd.  33,  88  pp.,  5  taf. 
Biitschli,  0.     1871.     Nahere  Mittheilungen  iiber  die  Entwicklung  und  den 

Bau  der  Samenfaden  der  Insecten.     Zeits.  wiss.  Zool,  bd.  21,  pp. 

526-534,  taf.  40,  41. 
Nusbaum,  J.     1882.     Zur  Entwickelungsgeschichte  der  Ausfiihrungsgange 

der  Sexualdriisen  bei  den  Insecten.     Zool.  Anz.,  jbg.  5,  pp.  637- 

643. 
Palmen,  J.  A.     1883.     Zur  vergleicbenden  Anatomic  der  Ausfiihrungsgange 

der     Sexualorgane    bei     den     Insekten.      Vorlaufige     Mittheilung. 

]\Iorph.  Jahrb.,  bd.  9,  pp.  169-176. 
Will,  L.     1883.     Zur  Bildung  des  Eies  und  des  Blastoderms  bei  den  vivi- 
paren Aphiden.     Arbeit,   zool.-zoot.   Inst.   Univ.   Wiirzburg,  bd.  6, 

pp.  217-258,  taf.  16. 
Palmen,  J.  A.     1884.     Ueber  paarige  Ausfiihrungsgange  der  Geschlechts- 

organe  bei  Insecten.     Ein  morphologische  Untersuchung.     108  pp., 

5  taf.     Helsingfors. 
Gilson,  G.     1885.     fitude  comparee  de  la  spermatogenese  chez  les  Arthro- 

podes.     La  Cellule,  t.  i,  pp.  7-188,  pis.  1-8.* 
Schneider,  A.     1885.     Die  Entwicklung  der  Geschlechtsorgane  der  Insecten. 

Zool.  Beitr.  von  A.  Schneider,  bd.   i,  pp.  257-300,  4  taf.     Breslau. 
Spichardt,  C.     1886.     Beitrag  zur  Entwickelung  der  mannlichen  Genitalien 

und    ihrer    Ausfiihrgange   bei    Lepidopteren.     Verb,    naturh.    Ver 

Bonn,  jbg.  43,  pp.   1-34,  taf.   i. 
La   Valette  St.  George.      1886,    1887.      Spermatologische   Beitriige.      Arch. 

mikr.  Anat.,  bd.  27,  pp.   1-12,  taf.   i,  2;  bd.  28,  pp.   1-13,  taf.   1-4; 

bd.  30,  pp.  426-434,  taf.  25. 


438  ENTOMOLOGY 

Von   Wielowiejski,   H.   R.     1886.     Zur   ^Morphologic   des   Insectenovariums. 

Zool.  Anz.,  jhg.  9,  pp.   132-139. 
Korschelt,  E.     1887.     Ueber  einige  interessante  Vorgange  bei  der  Bildung 

der  Insekteneier.     Zeits.  wiss.  Zool.,  bd.  45,  pp.  327-397,  taf.  18,  19. 
Nassonow,  N.     1887.     The  IMorphology  of  Insects  of  Primitive  Organiza- 
tion.    Studies  Lab.  Zool.  ]Mus.  ]\Iosco\v,  pp.  15-86,  2  pis.,  68  figs. 

(In  Russian.) 
Oudemans,  J.  T.     1888.     Beitrage  zur  Kenntniss  der  Thysanura  und  Col- 

lembola.     Bijdr.  Dierk.,  pp.   147-226.  taf.   1-3.     Amsterdam. 
Bertkau,  P.     1889.     Beschreibung  eines  Zwitters  von  Gastropacha  quercus, 

nebst    allgemeinen    Bemerkungen    und    einem    Verzeichniss    der 

beschriebenen  Arthropodenzwitter.    Archiv  Naturg.,  jhg.  55,  bd.  i, 

pp.  75-116,  figs.  1-3.* 
Leydig,  F.     1889.     Beitrage  zur  Kenntniss  des  thierischen   Eies   im  unbe- 

fruchteten   Zustande.     Zool.   Jahrb.,   Abth.   Anat.    Ont.,   bd.   3,   pp. 

287-432,  taf.  11-17. 
Lowne,  B.  T.     1889.     On  the   Structure  and   Development  of  the  Ovaries 

and  their  Appendages  in  the  Blowfly  (Calliphora  erythrocephala). 

Journ.  Linn.  Soc.  Zool.,  vol.  20,  pp.  418-442,  pi.  28.* 
Ballowitz,   E.     1890.     Untersuchungen   iiber    die    Struktur   der    Spermato- 

zoen,  zugleich  ein  Beitrag  zur  Lehre  vom  feineren  Bau  der  kon- 

traktilen    Elemente.     Die    Spermatozoen    der    Lisekten.     (L  Cole- 

opteren.)     Zeits.  wiss.  Zool.,  bd.  50,  pp.  317-407,  taf.   12-15. 
Henking,  H.     1890-92.     Untersuchungen  iiber  die  ersten  Entwicklungsvor- 

gange  in  der  Eiern  der  Insekten.     Zeits.  wiss.  Zool.,  bd.  49,  pp. 

503-564,   taf.   24-26;   bd.   51,  pp.   685-736,   taf.   35-37;   bd.   54,  pp. 

1-274.  taf.  1-12.  figs.  1-12. 
Ritter,  R.     1890.     Die   Entwicklung  der   Geschlechtsorgane  und   des   Dar- 

mes  bei   Chironomus.     Zeits.   wiss.   Zool.,  bd.   50,  pp.  408-427,  taf. 

16. 
Heymons,  R.      1891.      Die  Entwicklung  der  weiblichen  Geschlechtsorgane 

von   Phyllodromia    (Blatta)    germanica  L.     Zeits.   wiss.   Zool.,  bd. 

53,  pp.  434-536,  taf.   18-20. 
Koschewnikoff,  G.     1891.     Zur  Anatomic  der  mannlichen  Geschlechtsorgane 

der  Honigbiene.     Zool.  Anz.,  jhg.  14,  pp.  393-396. 
Ingenitzky,  J.      1893.      Zur   Kenntnis   der   Begattungsorgane   der   Libellu- 

liden.     Zool.  Anz.,  jhg.   16,  pp.  405-407,  2  figs. 
Escherich,  K.     1894.     Anatomische   Studien   fiber   das   mjinnliche   Genital- 
system  der  Coleoptcren.     Zeits.   wiss.   Zool.   bd.   57,   pp.   620-641, 

taf.  26,  figs.  1-3. 
Toyama,   K.     1894.     On    the    Spermatogenesis    of   the    Silk    Worm.     Bull. 

Coll.  Agr.  Univ.  Tokyo,  vol.  2,  pp.   125-157.  pis.  3,  4. 
Verson,  E.     1894.     Zur  Spermatogenesis  bei  der  Seidenraupe.     Zeits.  wiss. 

Zool.,  bd.  58,  pp.  303-313.  taf.   17. 
Kluge,  M.  H.  E.     1895.     Das  mannliche  Geschlechtsorgan  von  Vespa  ger- 
manica.    Archiv  Naturg.,  jhg.  61,  bd.  i,  pp.  159-198,  taf.  10. 
Peytoureau,  A.     1895.     Contributions  a  I'etude  de  la  morphologic  de  I'ar- 

mure  genitale  des  Insectes.     248  pp.,  22  pis.,  43  figs.     Paris. 


LITERATURE  439 

Wilcox,  E.  V.  1895.  Spermatogenesis  of  Caloptcnus  fenuir-rubi-um  and 
Cicada   libicen.     Bull.    Mus.    Comp.    ZooL,    vol.    27,   pp.    1-32,   pis. 

Wilcox,  E.  V.  1896.  l""urtlicr  Studies  on  the  Spermatogenesis  of  Calop- 
tcnus fcmur-rubruin.  Bull.  Mus.  Comp.  Zool,  vol.  29,  pp.  193- 
_'o_'.  pis.    1-3. 

Fenard,  A.  1897.  Recherches  sur  les  organes  complementaires  internes 
de  I'appareil  genital  des  Orthoptcres.  Bull.  sc.  France  Belgique, 
t.  29,  pp.  390-533.  pis.  24-28. 

Gross,  J.  1903.  Untersuchungen  iiber  die  Histologic  des  Insectenovari- 
ums.     Zool.  Jahrb.,  Abth.  Anat.  Ont.,  bd.  18,  pp.  71-186,  taf.  6-14.* 

Griinberg,  K.  1903.  Untersuchungen  iiber  die  Keim-  und  Niihrzellen  in 
den  Hoden  und  Ovarien  der  Lepidoptera.  Zeits.  wiss.  Zool.,  bd. 
74,  pp.  327-395.  taf.  i(>-i8. 

Holmgren,  N.  1903.  Ueber  vivipare  Insecten.  Zool.  Jahrb.,  bd.  19,  pp. 
431-468,  10  figs.* 

EMBRYOLOGY 

Rathke,  H.     1844.    Ueber  die  Eier  von  Gryllotalpa  und  ihre  Entwickelung. 

Miiller's  Archiv  Anat.  Phys.,  bd.  2,  pp.  27-37,  figs.  1-5. 
Meyer,  G.  H.     1848.     Ueber   Entw^icklung  des   Fettkorpers,  der  Tracheen 

und  der  keimbereitenden  Geschlechtstheile   bei   den  Lepidopteren. 

Zeits.  wiss.  Zool,  bd.  i.  pp.  175-197,  4  taf. 
Leuckart,  R.      1858.      Die  Fortpflanzung  und  Entwicklung  der   Pupiparen 

nach  Beobachtungen  an  Melophagus  ovinus.     Abh.  naturf.  Gesell. 

Halle,  bd.  4,  pp.  145-226,  3  taf. 
Weismann,  A.     1863.     Die  Entwicklung  der  Dipteren  im  Ei,  nach  Beobacht- 
ungen  an   Chironomus   spec,   Musca   vomitoria   und    Pulex   canis. 

Zeits.  wiss.  Zool.,  bd.   13,  pp.   107-220,  7  taf.     Separate,   1864,  263 

pp.,  14  taf. 
Metschnikoff,  E.     1866.     Embryologische  Studien  an  Insecten.     Zeits.  wiss. 

Zool,  bd.  16,  pp.  389-500,  10  taf. 
Brandt,   A.     1869.     BeitrJige   zur   Entwicklungsgeschichte    der   Libelluliden 

und   Hemipteren.     Mem.   Acad.   St.  Petersbourg.  ser.  7,  t.   13,  pp. 

1-33.  3  pis. 
Melnikow,   N.      1869.      Beitrage   zur   Embryonalentwicklung  der   Insekten. 

Archiv  Naturg.,  jhg.  35,  bd.  i,  pp.   136-189,  4  taf. 
Biitschli,   0.     1870.     Zur   Entwicklungsgeschichte    der    Biene.     Zeits.    wiss. 

Zool,  bd.  20,  pp.  519-564,  taf.  24-27. 
Kowalevsky,    A.     1871.     Embryologische    Studien    an    Wiirmern    und    Ar- 

thropoden.     Mem.   Acad.   St.   Petersbourg,  ser.   7,  t.    16,   pp.    1-70, 

12  pis. 
Dohrn,  A.     1875.     Notizen  zur  Kenntniss   der  Insectenentwicklung.     Zeits. 

wiss.  Zool.,  bd.  26,  pp.  1 12-138. 
Batschek,   B.      1877.      Beitrage   zur'  Entwicklungsgeschichte   der   Lepidop- 
teren.    Jenais.  Zeits.  Naturw.,  bd.  n.  38  pp.,  3  taf.,  2  tigs. 


440  ENTOMOLOGY 

Bobretzky,  N.     1878.     Ueber  die  Bildung  des  Blastoderms  und  der  Keim- 

blatter  bei   den   Insecten.     Zeits.   wiss.   Zool.,   bd.   31,   pp.    195-215, 

taf.   14. 
Korotneff,    A.      1883.      Entwicklung    des    Herzens    bei    Gryllotalpa.     Zool. 

Anz.,  jhg.  6,  pp.  687-690,  figs.  I,  2. 
Packard,   A.   S.      1883.      The   Embryological   Development   of   the   Locust. 

Third  Rept.  U.  S.  Ent.  Comm.,  pp.  263-285,  pis.  16-21,  figs.  lo-ii. 

Washington. 
Will,  L.     1883.     Zur  Bildung  des  Eies  und  des  Blastoderms  bei  den  vivi- 

paren  Aphiden.     Arbeit,  zool.-zoot.   Inst.   Univ.  Wiirzburg,  bd.   6. 

pp.  217-258,  taf.  16. 
Ayers,  H.     1884.     On  the  Development  of  QScanthus  niveus  and  its  Para- 
site Teleas.     ]Mem.  Bost.  Soc.  Nat.  Hist.,  vol.  3,  pp.  225-281,  pis. 

18-25,  figs.  1-41.* 
Patten,  W.     1884.     The  Development  of   Phryganids,  with  a   Preliminary 

Note   on   the   Development   of    Blatta   germanica.      Quart.   Journ. 

Micr.  Sc,  vol.  24  (n.  s.),  pp.  549-602,  pis.  36a,  b,  c. 
Witlaczil,   E.      1884.      Entwicklungsgeschichte   der   Aphiden.      Zeits.    wiss. 

Zool,  bd.  40,  pp.  559-696,  taf.  28-34.* 
Korotneff,  A.     1885.     Die  Embrj^ologie  der  Gryllotalpa.     Zeits.  wiss.  Zool, 

bd.  41,  pp.  570-604,  taf.  29-31. 
Schneider,   A.     1885.     Ueber   die   Entwicklung   der   Geschlechtsorgane   der 

Insecten.      Zool.    Beitr.    von    A.    Schneider,   bd.    i,   pp.    257-300,   4 

taf.     Breslau. 
Blochmann,     F.      1887.      Ueber     die    Richtungskorper     bei     Insecteneiern. 

iNIorph.  Jahrb.,  bd.   12,  pp.  544-574,  taf.  26,  27. 
Biitschli,   0.      1888.      Bemerkungen   iiber   die   Entwicklungsgeschichte   von 

[Nlusca.     ]\Iorph.  Jahrb.,  bd.  14,  pp.  170-174,  3  figs. 
Cholodkovsky,   N.      1888.      Ueber   die    Bildung  des   Entoderms   bei   Blatta 

germanica.     Zool.  Anz.,  jhg.   11,  pp.   163-166,  figs,   i,  2. 
Graber,  V.     1888.     Ueber  die  Polypodie  bei  Insekten-Embryonen.     Morph. 

Jahrb..  bd.  13,  pp.  586-615,  taf.  25,  26. 
Graber,  V.     1888.     Ueber  die  primare   Segmentirung  des   Keimstreifs   der 

Insekten.     Morph.  Jahrb.,  bd.  14,  pp.  345-368,  taf.  14,  15,  4  figs. 
Henking,   H.     1888.     Die   ersten   Entwicklungsvorgange    im   Fliegenei   und 

freie  Kernbildung.     Zeits.  wiss.  Zool.,  bd.  46,  pp.  289-336,  taf.  23- 

26,  3  figs. 
Will,    L.      1888.      Entwicklungsgeschichte    der    viviparen    Aphiden.      Zool. 

Jahrb.,  Abth.  Anat  Ont.,  bd.  3,  pp.  201-286,  taf.  6-10. 
Cholodkovsky,  N.     1889.     Studien   zur  Entwicklungsgeschichte   der   Insek- 
ten.    Zeits.  wiss.  Zool.,  bd.  48,  pp.  89-100,  taf.  8. 
Graber,  V.     1889.     Ueber  den  Bau  und  die  phylogenetische  Bedeutung  der 

embryonalen  Bauchanhange  der  Insekten.     Biol.  Centralb.,  jhg.  9, 

PP-  355-363- 
Heider,  K.     1889.     Die   Embryonalentwicklung  von   Hydrophilus  piceus  L.. 

I.  Theil.     98  pp.,  13  taf.,  9  figs.     Jena. 


LITERATURE  44^ 

Leydig,  F.     1889.     Beitriigc  zur   Kenntniss  dcs  thicrischen   Eies   im  unbc- 

fnichteten   Zustande.     Zool.   Jahrb.,   Abth.   Anat.    Out.,   bd.   3,   pp. 

287-43J,  taf.   11-17. 
Nusbaum,  J.     iSSg.     Zur  l-'rasc  dcr  Scgmentierung  des  Keimstreifens  und 

der   Bauchanhangc   dcr   Insektenembryoncn.     Biol.   Centralb.,   jhg. 

9,  pp.  516-522,  fig.  I. 
Voeltzkow,  A.     1889.     Entwickelung  ini  lu  von  Mu.sca  vomitoria.     Arbeit. 

zool.-zoot.  Inst.   Uni\-.  Wiirzbnrg,  bd.  9,  pp.  1-48,  taf.   1-4. 
Voeltzkow,  A.     1889.     ]\Iekjlontlia  vulgaris.     Ein  Beitrag  zur  Entwickelung 

ini  Ei  bci  Insckten.     Arbeit,  zool.-zoot.  Inst.  Univ.  Wiirzburg,  bd. 

9,  pp.  49-64,  taf.  5. 
Wheeler,  W.  M.     1889.     The  Embryology  of  Blatta  germanica  and   Dory- 

phora   decemlineata.     Journ.   JNIorph.,   vol.   3,  pp.   291-386,  pis.    15- 

21,  figs.   1-16. 
Carriere,  J.     1890.     Die  Entwicklung  der  Mauerbiene    (Chalicodoma  mur- 

aria   I\-d)r.)    im   Ei.     Archiv  mikr.  Anat.,  bd.   35,  pp.    141-165.  taf. 

8,  8a. 
Henking,  H.     1890-92.     Untersuchungen  iiber  die  ersten  Entwicklungsvor- 

giinge   in  der   Eiern   der   Insckten.     Zeits.   wiss.   Zool.,  bd.   49,   pp. 

503-564,   taf.    24-26;    bd.   51.   pp.    685-736,   taf.    35-37;    bd.    54,   PP- 

1-274,  taf.   1-12,  figs.    1-12. 
Nusbaum,  J.     1890.     Zur   Frage   der   Rtickenbildung  bei   den   Insektenem- 
bryoncn.    Biol.  Centralb.,  jhg.   10,  pp.   110-114. 
Ritter,   R.     1890.     Die   Entwicklung  der   Geschlechtsorgane   und   des   Dar- 

mes  bei   Chironomus.     Zeits.  wiss.   Zool,  bd.   50,  pp.  408-427,   taf. 

16. 
Wheeler,  W.  M.     1890.     On  the  Appendages  of  the  Eirst  Abdominal  Seg- 
ment of  Embryo   Insects.     Trans.   Wis.  Acad.   Sc,  vol.  8,  pp.  87- 

140,  pis.   1-3.* 
Cholodkowsky,    N.     1891.     Die    Embryonalentwicklung    von    Phyllodromia 

(Blatta  germanica).     Mem.   Acad.   St.   Petersbourg,   ser.   7,   t.   38, 

4  -f  120  pp.,  6  pis.,  6  figs. 
Graber,  V.     1891.     Ueber  die  embryonale  Anlage  des  Blut-  und  Eettgewebes 

der  Insekten.     Biol.  Centralb.,  jhg.   11,  pp.  212-224. 
Wheeler,  W.  M.      1891.      Neuroblasts  in  the  Arthropod  Embryo.      Journ. 

Morph.,  vol.  4,  pp.  337-343,  i  fig- 
Graber,   V.      1892.      Ueber   die   morphologische    Bedeutung   der   ventralen 

Abdominalanhange  der  Insekten-Embryonen.     Morph.   Jahrb.,  bd. 

17,  pp.  467-482,  figs.   1-6. 
Korschelt,  E.,  und  Heider,  K.      1892.      Lehrbuch   der  vergleichenden   Ent- 

wicklungsgeschichte  der  wirbellosen  Thiere.     Heft  2,  pp.  761-890, 

figs.     Jena.*     Trans.  :     1899.     'Si.   Bernard  and   J\I.   F".   Woodward. 

Text-Book  of  the  Embryology  of  Invertebrates.     12  +  441  pp.,  198 

figs.     London,  Swan  Sonnenschein  &  Co.,  Ltd. ;   New  York,  The 

]Macmillan  Co.* 
Wheeler,  W.   M.      1893.      A   Contribution   to   Insect   Embryology.      Journ. 

Worph.,  vol.  8,  pp.  1-160,  pis.  1-6,  figs.  1-7. 


442  ENTOMOLOGY 

Heymons,  R.      1895.      Die   Embnonalentwickelung  von  Dermapteren  und 

Orthopteren  unter  besonderer  Beriicksichtigung  der  Keimblatter- 

bildung.     8+136  pp.,    12  taf.,   33  figs.     Jena. 
Heymons,   R.     1896.     Grundziige  der   Entwickelung  und   des   Korperbanes 

von   Odonaten   und   Ephemeriden.     Anh.   Abh.   Akad.   Wiss.    Ber- 
lin, 66  pp.,  2  taf. 
Heymons,  R.      1897.      Entwicklungsgeschichtliche   Untersuchungen   an  Le- 

pisma   saccharina  L.     Zeits.   wiss.   Zool.,   bd.   62,  pp.   583-631,   taf. 

-29,  30.  3  figs. 
Kulagin,    N.      1897.      Beitriige    zur    Kenntnis    der   Entwickkmgsgeschichte 

von  Platygaster.     Zeits.  wiss.  Zool,  bd.  63,  pp.  195-235,  taf.  10,  11. 
Claypole,  A.  M.     1898.     The  Embr3'olog3'  and  Oogenesis  of  Anurida  mari- 

tima   (Guer.).     Journ.  IMorph.,  vol.   14,  pp.  219-300,  pis.  20-25,   11 

figs. 
Uzel,  H.     1898.     Studien  iiber  die   Entwicklung  der  apterygoten   Insecten. 

6  +  58  pp.,  6  taf.,  5  figs.     Berlin. 
Wilson,  E.  B.      1900.      The   Cell  in  Development   and   Inheritance.      21  -j- 

483  pp.,  194  figs.     New  York  and  London.     The  Macmillan  Co. 

POSTEMBRYONIC   DEVELOPMENT.     METAMORPHOSIS 
Fabre,  J.  L.     1856.     fitude  sur  I'instinct  et  les  metamorphoses  des  Sphe- 

giens.     Ann.  Sc.  nat.  Zool.,  ser.  4,  t.  6,  pp.  137-189. 
Fabre,  J.  L.     1857.     Memoire  sur  I'hypermetamorphose  et  les  moeurs  des 

Meloides.     Ann.  Sc.  nat.  Zool.,  ser.  4,  t.  7,  pp.  299-365 ;  i  pi. ;  1858, 

t.  9,  pp.  265-276. 
Miiller,  F.      1864.      Fiir   Darwin.     Leipzig.     Translation:     Facts   and   Fig- 
ures in  aid  of  Darwin,  London,  1869. 
Weismann,   A.      1864.      Die    nachembryonale    Entwicklung    der    INIusciden 

nacli    Beobachtungen    an   Musca   vomitoria   und    Sarcophaga    car- 

naria.     Zeits.  wiss.  Zool.,  bd.   14,  pp.   187-336. 
Weismann,    A.      1866.      Die     Metamorphose    von    Corethra    plumicornis. 

Zeits.  wiss.  Zool.,  bd.   16,  pp.  45-127,  5  taf. 
Trouvelot,  L.     1867.     The  American  Silk  Worm.     Amer.   Nat.,  vol.   i,  pp. 

30-38,  85-94,  145-149,  -4  figs.,  pis.  5-  6. 
Brauer,  F.     1869.     Betrachtungen  iiber  die  Verwandlung  der  Insekten  im 

Sinne  der  Descendenz-Theorie.     Verb,  zool.-bot.  Gesell.  Wien,  bd. 

19,  pp.  299-318;  bd.  28   (1878),  1879.  pp.   151-166. 
Ganin,    M.      1869.      Beitriige    zur    Kenntniss    der    Entwickelungsgeschichte 

bei  den  Insecten.     Zeits.  wiss.  Zool.,  bd.   19,  pp.  381-451,  3  taf. 
Chapman,   T.   A.      1870.      On    the    Parasitism   of   Rhipiphorus   paradoxus. 

Ann.  I\Iag.   Nat.  Hist.,  ser.  4,  vol.  5,  pp.   191-198. 
Chapman,   T.   A.     1870.     Some    Facts    towards   a   Life    History   of   Rhipi- 
phorus paradoxus.     Ann.  Mag.   Nat.  Hist.,  ser.  4,  vol.  6,  pp.  314- 

326,  pi.   16. 
Landois,   H.     1871.     Beitriige    zur   Entwickkmgsgeschichte   der    Schmetter- 

lingsfliigel  in  der  Raupe  und  Puppe.     Zeits.  wiss.  Zool.,  bd.  21,  pp. 

305-316,  taf.  23. 


LITERATURE  443 

Packard,  A.  S.     1873.     Our  Common  Insects.     225  pp..  268  figs.     Boston. 

Estes  and  Lauriat. 
Lubbock,  J.     1874,   1883.     On  the   Origin   and   Metamorphoses   of   Insects. 

16 -|-  108  pp.,  6  pis.,  63  figs.     London.     Macmillan  &  Co. 
Ganin,  M.     1876.     [Materials  for  a  Knowledge  of  the  Postembryonal  De- 
velopment   of     Insects.      Warsaw.]      (In     Russian.)      Abstracts: 

Anier.   Nat.,  vol.   11,   1877,  pp.  423-430;   Zeits.  wiss.   Zool.,  bd.   28, 

1877,  pp.  386-389. 
Riley,  C.  V.     1877.     On  the  Larval  Characters  and  Habits  of  the  Blister- 
beetles   belonging  to   the    Genera    Macrobasis   Lee.   and    Epicauta 

Fabr. ;   with  Remarks  on  other   Species  of  the  Family   Meloidse. 

Trans.  St.  Loui.?  Acad.  Sc,  vol.  3,  pp.  544-562,  figs.  35-39,  pi.  5. 
Dewitz,   H.      1878.      Beitriige   zur   Kenntniss   der  postembrj'onalen    Glied- 

massenbildung  bei  den  Insecten.     Zeits.  wiss.  Zool.,  bd.  30,  suppl., 

pp.  7S-105,  taf.  5. 
Packard,  A.   S.     1878.     Metamorphoses    [of   Locusts].     First    Rept.   U.    S. 

Ent.  Comm.,  pp.  279-284,  pis.   1-3,  figs.   19,  20. 
Dewitz,   H.     1881.     Ueber   die    Fliigelbildung   bei    Phryganidcn    und    Lepi- 

dopteren.     Berl.  ent.  Zeits.,  bd.  25,  pp.  53-60,   taf.  3,  4. 
Metschnikoff,   E.     1883.     Lhitersuchungen   fiber  die   intracellulare   Verdau- 

ung  bei   wirbellosen   Thieren.     Arb.    zool.    Inst.    Wien,   bd.    5,   pp. 

141-168,  taf.   13,   14. 
Viallanes,  H.     1883.     Recherches   sur  I'histologie   des   Insectes   et   sur   les 

phenomenes    histologiques    qui    accompagnent    le    developpement 

post-embryonnaire  de  ces  animaux.     x\nn.  Sc.  nat.  Zool.,  ser.  6,  t. 

14,  348  pp.,   18  pis. 
"Von    Wielowiejsky,    H.    R.      1883.      Ueber    den    Fettkorper    von    Corethra 

plumicornis  und   seine  Entwicklung.     Zool.   Anz.,  jhg.  6,  pp.  318- 

322. 
Kowalevsky,  A.      1885.      Beitnige   zur  nachembryonalen   Entwicklung  der 

Musciden.     Zool.  Anz.,  jhg.  8,  pp.  98-103,  123-128,  153-157. 
Schmidt,  0.     1885.     Metamorphose  und  Anatomic  des  mannlichen  Aspidi- 

otus  nerii.     Archiv  Naturg.,  jhg.  51,  bd.   i,  pp.   169-200,  taf.  9,   10. 
Witlaczil,  E.     1885.     Zur  Morphologic  und  Anatomic  der  Cocciden.     Zeits. 

wiss.  Zool.,  bd.  43,  pp.  149-174,  taf.  5. 
Kowalevsky,  A.     1887.     Beitrage  zur  Kenntniss  der  nachembryonalen  Ent- 
wicklung  der   Musciden.     Zeits.   wiss.    Zool,   bd.   45,   pp.    542-594, 

taf.  26-30. 
Van   Rees,   J.     1888.     Beitrage    zur    Kenntnis    der    inneren    Metamorphose 

von  Musca  vomitoria.     Zool.  Jahrb.,  Abth.  Anat.   Ont..  bd.  3,  pp. 

1-134,  taf.   I,  2,   14  figs. 
Hyatt,  A.,  and  Arms,  J.  M.     1890.     Insecta.     23 -|- 300  pp.,  13  pis.,  223  figs. 

Boston.     D.  C.  Heath  &  Co.* 
Bugnion,  E.     1891.     Recherches   sur  le   developpement   post-embryonnaire. 

I'anatomie,    et    les    moeurs    de    I'Encyrtus    fuscicollis.      Rec.    zool. 

Suisse,  t.  5,  pp.  435-534.  pis.  20-25. 


444  ENTOMOLOGY 

Poulton,    E.    B.     iSgi.     The    External    Morphology    of    the   Lepidopterous 

Pupa  :    its  Relation  to  that  of  the  other  Stages  and  to  the  Origin 

and   History  of  Metamorphosis.     Trans.   Linn.   Soc.   Zool.,   ser.   2, 

vol.  5,  pp.  245-263,  pis.  26.  27. 
Korschelt,   E.,   und   Heider,   K.     1892.     Lehrbuch    der   vergleichenden    Ent- 

wicklungsgeschichte  der  wirbellosen  Thiere.     Heft  2,  pp.  761-890, 

figs.     Jena.* 
Miall,  L.  C,  and  Hammond,  A.  R.     1892.     The  Development  of  the  Head 

of  Chironomus.     Trans.  Linn.   Soc.   Zool,   ser.  2,  vol.   5,  pp.  265- 

279,  pis.  28-31. 
Pratt,   H.   S.     1893.     BeitrJige   zur   Kenntnis   der    Pupiparen.     Archiv    Na- 

turg.,  jhg.  59,  bd.   I,  pp.   151-200,  taf.  6. 
Gonin,  J.     1894.     Recherches  sur  la  metamorphose  des  Lepidopteres.     De 

la  formation  des  appendices  imaginaux  dans  la  chenille  du  Pieris 

brassicae.     Bull.  Soc.  vaud.   Sc.  nat.,  t.  30,  pp.   1-52,  5  pis. 
Miall,  L.  C.     1895.     The  Transformations  of  Lisects.     Nature,  vol.  53,  pp. 

153-158. 
Hyatt,  A.,  and  Arms,  J.  M.     1896.     The  Meaning  of  Metamorphosis.     Nat. 

Sc,  vol.  8,  pp.  395-403- 
Kulagin,    N.     1897.     Beitrage    zur    Kenntnis    der    Entwicklungsgeschichte 

von  Platygaster.     Zeits.  wiss.  Zool.,  bd.  63,  pp.  195-235,  taf.  10,  11. 
Packard,  A.  S.     1897.     Notes  on  the  Transformations  of  Higher  Hymen- 

optera.     Journ.  N.  Y.  Ent.  Soc,  vol.  4,  pp.   155-166,  figs.  1-5;  vol. 

5,  pp.  77-87.  109-120,  figs.  6-13. 
Pratt,  H.  S.     1897.     Imaginal  Discs  in  Insects.     Psyche,  vol.  8,  pp.    15-30, 

IT    figs. 

Packard,   A.   S.     1898.     A   Text-Book   of   Entomology.     17 -|- 729   pp.,   654 

ligs.     New  York  and  London.     The  Macmillan  Co. 
Boas,  J.   E.   V.     1899.     Einige   Bemerkungen   fiber  die   Metamorphose   der 

Insecten.     Zool.   Jahrb.,   Abth.   Syst.,   bd.    12,   pp.   385-402,   taf.   20, 

figs.  1-3. 
Lameere,  A.     1899.     La  raison  d'etre  des  metamorphoses  chez  les  Insectes. 

Ann.  Soc.  ent.  Belg.,  t.  43,  pp.  619-636. 
Perez,  C.     1899.    Sur  la  metamorphose  des  insectes.     Bull.  Soc.  ent.  France, 

pp.  398-402. 
Wahl,  B.     1901.     Ueber  die  Entwicklung  der  hypodermalen  Imaginalschei- 

ben  im  Thorax  und  Abdomen  der  Larve  von  Eristalis  Latr.     Zeits. 

wiss.  Zool.,  bd.  70,  pp.  171-191,  taf.  9,  figs.  1-4. 
Perez,    C.     1902.     Contribution    a    I'etude    des    metamorphoses.     Bull.    sc. 

France  Belg.,  t.  37,  pp.  195-427,  pis.  10-12,  32  figs. 
Deegener,    P.      1904.      Dfe     Entwicklung    des     Darmcanals    der     Insecten 

wahrend  der  Metamorphose.     Zool.  Jahrb.,  Abth.  Anat.  Out.,  bd. 

20,  pp.  499-676,  taf.  33-43* 
Powell,  P.  B.     1904-05.     The   Development   of   Wings   of  Certain   Beetles, 

and  some  Studies  of  the  Origin  of  the  Wings  of  Insects.     Journ 

N.  Y.  Ent.  Soc,  vol.  12,  pp.  237-243,  pis.  11-17;  vol.  13,  pp.  5-22.=^ 


LITERATURE  445 


AQUATIC   INSECTS 
Dufour,   L.      1849.      Des   divers   modes   de   respiration    aqualique    dans   les 

inscctes.     Compt.  rend.  Acad.  Sc,  t.  29,  pp.  yC.W/O-     Ann.  Mag. 

Nat.  Hist,  ser.  2,  vol.  6,  1850,  pp.  112-118. 
Dufour,  L.      1852.      fitudes  anatomiques  et  physiologiques  et  observations 

sur  les  larves  des  Libellules.     Ann.  Sc.  nat.  Zool.,  ser.  3,  t.  17,  pp. 

65-1 10,  3  pis. 
Hagen,    H.   A.      1853.      Leon    Dnfonr    iibcr    die    Larvcn    der    Lil^ellen    mit 

Beriicksichtigung  der  friiiiercn  Arbciten.      (Ucbcr  Respiration  der 

Insecten.)     Stett.  cnl.  Zeit.,  bd.    14,  pp.  9S-106,  237-238,  260-270, 

311-325,  334-34(^- 

Williams,  T.  1853-57.  On  tbe  Mecbanism  of  Aquatic  Respiration  and  on 
tbe  Structure  of  tbe  Organs  of  Breatbing  in  Invertebrate  Ani- 
mals.    Ann.  Mag.  Nat.  Hist.,  ser.  2,  vols.  12-19,  17  pis. 

Oustalet,  E.  1869.  Note  sur  la  respiration  cbez  les  nynipbes  des  Libel- 
lules.    Ann.  Sc.  nat.  Zool.,  ser.  5,  t.  11,  pp.  370-386,  3  pis. 

Sharp,  D.  1877.  Observations  on  the  Respiratory  Action  of  the  Carniv- 
orous Water  Beetles  (Dytiscidae).  Journ.  Linn.  Soc.  Zool,  vol. 
13,  pp.  161-183. 

Poletajew,  0.  1880.  Quelques  mots  sur  les  organes  respiratoires  des  lar- 
ves des  Odonates.     Horse  Soc.  Ent.  Ross.,  t.  15,  pp.  436-4S2,  2  pis. 

Vayssiere,  A.  1882.  Recherches  sur  Torganisation  des  larves  des  Ephe- 
merines.     Ann.  Sc.  nat.  Zool.,  ser.  6,  t.  13,  pp.  i-i37,  pls-  i-H- 

Macloskie,  G.  1883.  Pneumatic  Functions  of  Insects.  Psyche,  vol.  3,  pp. 
375-378. 

White,  F.  B.  1883.  Report  on  the  Pelagic  Hemiptera.  Rept.  Sc.  Res. 
Voy.  H.  M.  S.  Challenger,  1873-1876,  Zoology,  vol.  7,  82  pp.,  3  pis. 

Comstock,  J.  H.  1887.  Note  on  Respiration  of  Aquatic  Bugs.  Amer. 
Nat.,  vol.  21,  pp.  577-578. 

Schwedt,  E.  1887.  Ueber  Athmung  der  Larven  und  Puppen  von  Donacia 
crassipes.     Bed.  ent.  Zeits.,  bd.  31,  pp.  325-334,  taf.  5b. 

Amans,  P.  C.  1888.  Comparaisons  des  organes  de  la  locomotion  aqua- 
tique.     Ann.  Sc.  nat.  Zool,  ser.  7,  t.  6,  pp.  1-164,  pis.  1-6. 

Dewitz,  H.  1888.  Entnebmen  die  Larven  der  Donacien  vermittelst  Stig- 
men  oder  Athemrohren  den  Luftraumen  der  Pflanzen  die  sauer- 
stofifbahige  Luft?     Berl.  ent.  Zeits.,  bd.  32,  pp.  5-6,  2  figs. 

Garman,  H.  1889.  A  Preliminary  Report  on  the  Animals  of  the  Missis- 
sippi Bottoms  near  Quincy,  Illinois,  in  August,  1888.  Bull.  111. 
St.  Lab.  Nat.  Hist.,  vol.  3,  pp.  123-184. 

Moniez,  R.  1890.  Acariens  et  Insectes  marins  des  cotes  du  Boulonnais. 
Rev.  biol.  nord  France,  t.  2,  pp.  321,  etc. 

Miall,  L.  C.  1891.  Some  Difficulties  in  the  Life  of  Aquatic  Insects.  Na- 
ture, vol.  44,  pp.  457-462. 

Walker,  J.  J.  1893.  On  the  Genus  Halobates,  Escb.,  and  other  Marine 
Hemiptera.     Ent.  Mon.  Mag.,  ser.  2,  vol.  4  (29),  pp.  2.2'j-2i2. 

Carpenter,  G.  H.     1895.     Pelagic  Hemiptera.     Nat.  Sc,  vol.  7,  pp.  60-61. 


446  ENTOMOLOGY 

Hart,  C.  A.     1895.     On  the  Entomologj'  of  the  IlHnois  River  and  Adjacent 

Waters.     Bull.   111.    St.    Lab.    Nat.    Hist.,   vol.   4,   pp.    149-273,   pis. 

I-I5- 
Miall,  L.  C.     1895,  1903.     The  Natural  History  of  Aquatic  Insects.     11 -f 

395  PP-.  116  figs.     London  and  New  York.     Macmillan  &  Co.* 
Sadones,  J.      1895.      L'appareil   digestif   et   respiratoire   larvaire   des   Odo- 

nates.     La  Cellule,  t.  11,  pp.  271-325,  pis.  1-3. 
Gilson,   G.,   and   Sadones,   J.      1896.      The   Larval    Gills   of   the    Odonata. 

Journ.  Linn.  Soc.  Zool.,  vol.  25,  pp.  413-418,  figs.  1-3. 
Comstock,  J.   H.     1897,   1901.     Insect   Life.     6  +  349  pp.,   18  pis.,   296  figs. 

New  York.     D.  Appleton  &  Co.* 
Needham,   J.    G.      1900.      Insect    Drift   on    the    Shore    of   Lake    Michigan. 

Occas.  Mem.  Chicago  Ent.  Soc,  vol.   i,  pp.  1-8,  i  fig. 
Needham,  J.  G.,  and  Betten,  C.     1901.     Aquatic  Insects  in  the  Adirondacks. 

Bull.  N.  Y.  St.  ]\Ius.,  no.  47,  pp.  383-612,  36  pis.,  42  figs. 
Needham,  J.  G.,  MacGillivray,  A.  D.,  Johannsen,  0.  A.,  and  Davis,  K.  C. 

1903.     Aquatic  Insects  in  New  York  State.     Bull.  N.  Y.  St.  Mus., 

no.  68,  321  pp.,  52  pis.,  26  figs.* 

COLOR   AND    COLORATION 

Dorfmeister,  G.  1864.  LTeber  die  Einwirkung  verschiedener,  wahrend 
den  Entwicklungsperioden  angewendeter  Warmegrade  auf  die 
Farbung  und  Zeichnung  der  Schmetterlinge.  Mitth.  naturw.  Ver. 
Steiermark,  pp.  99-108,  I  taf. 

Landois,  H.  1864.  Beobachtungen  iiber  das  Blut  der  Insecten.  Zeits. 
wiss.  Zool.,  bd.  14,  pp.  55-70,  taf.  7-9. 

Wood,  T.  W.  1867.  Remarks  on  the  Coloration  of  Chr3'salides.  Trans. 
Ent.  Soc.  London,  ser.  3,  vol.  5,  Proc,  pp.  99-101. 

Higgins,  H.  H.  1868.  On  the  Colour-Patterns  of  Butterflies.  Quart. 
Journ.  Sc,  vol.  5,  pp.  323-329,  i  pi. 

Weismann,  A.  1875.  Studien  zur  Descendenztheorie.  I.  Ueber  den 
Saison  Dimorphismus  der  Schmetterlinge.  Leipzig.  Trans.: 
1880-81.  R.  Meldola.  Studies  in  the  Theory  of  Descent.  554 
pp.,  8  pis.     London. 

Scudder,  S.  H.  1877.  Antigeny,  or  Sexual  Dimorphism  in  Butterflies. 
Proc.  Amer.  Acad.  Arts  Sc.  vol.  12,  pp.  150-158. 

Dorfmeister,  G.  1880.  Ueber  den  Einfluss  der  Temperatur  bei  der  Erzeu- 
gung  der  Schmetterlingsvarietaten.  Mitth.  naturw.  Ver.  Steier- 
mark, jhg.  1879,  PP-  3-8,  I  taf. 

Scudder,  S.  H,  1881.  Butterflies;  their  Structure,  Changes  and  Life- 
Histories,  with  Special  Reference  to  American  Forms.  9  -|-  322 
pp.,  201  figs.     New  York.     Henry  Holt  &  Co. 

Hagen,  H.  A.  1882.  On  the  Color  and  the  Pattern  of  Insects.  Proc. 
Amer.  Acad.  Arts  Sc,  vol.  17,  pp.  234-267. 

Dimmock,  G.  1883.  The  Scales  of  Coleoptera.  Psyche,  vol.  4,  pp.  3-1 1, 
23-27,  43-47,  63-71,   II  figs.* 


LITERATURE  447 

Krukenberg,  C.  F.  W.  1884.  [Colors  and  Pigments  of  Insects.]  Ent. 
Nachr.,  jhg.  10,  pp.  291-296. 

Poulton,  E.  B.  1884.  Notes  upon,  or  suggested  by  the  Colours,  Markings 
and  Protective  Attitudes  of  certain  Lepidoptcrous  Larvce  and 
Pupje,  and  of  a  phytophagous  hymenopterous  larva.  Trans.  Ent. 
Soc.  London,  pp.  27-60,  pi.  i. 

Poulton,  E,  B.  1885.  The  Essential  Nature  of  the  Colouring  of  Phytopha- 
gous Larvae  and  their  Pupre,  etc.  Proc.  Roy.  Soc.  London,  vol. 
38,  pp.  269-315- 

Poulton,  E.  B.  1885.  Further  Notes  upon  the  Markings  and  Attitudes  of 
Lepidoptcrous  Larvae.     Trans.  Ent.  Soc.  London,  pp.  281-329,  pi.  7. 

Poulton,  E.  B.  1887.  An  Enquiry  into  the  Cause  and  Extent  of  a  Special 
Colour-Relation  between  Certain  Exposed  Pupse  and  the  Surfaces 
which  immediately  surround  them.  Phil.  Trans.  Roy.  Soc.  Lon- 
don, vol.  178,  pp.  311-44T,  pi.  26. 

Chapman,  T.  A.  1888.  On  jNIelanism  in  Lepidoptera.  Ent.  Mon.  Mag., 
vol.  25,  p.  40. 

Dixey,  F.  A.  1890.  On  the  Phylogenetic  Significance  of  the  Wing-Mark- 
ings in  certain  Genera  of  the  Nymphalidas.  Trans.  Ent.  Soc.  Lon- 
don, pp.  89-129,  pis.  1-3. 

Merrifield,  F.  1890.  Systematic  temperature  experiments  on  some  Lepi- 
doptera in  all  their  stages.  Trans.  Ent.  Soc.  London,  pp.  131-159, 
pis.  4.  5- 

Poulton,  E.  B.  1890.  The  Colours  of  Animals.  13-1-360  pp.,  i  pi.,  66 
figs.     New  York.     D.  Appleton  &  Co. 

Seitz,  A.  1890,  1893.  Allgemeine  Biologic  der  Schmetterlinge.  Zool. 
Jahrb.,  Abth.  Syst.,  etc.,  bd.  5,  pp.  281-343;  bd.  7,  pp.  131-186.* 

Coste,  F.  H.  P.  1890-91.  Contributions  to  the  Chemistry  of  Insect  Colors. 
Entomologist,  vol.  23,  pp.  128-132,  etc. ;  vol.  24,  pp.  9-15,  etc. 

Hopkins,  F.  G.  1891.  Pigment  in  Yellow  Butterflies.  Nature,  vol.  45, 
pp.  197-198. 

Merrifield,  F.  1891.  Conspicuous  effects  on  the  markings  and  colouring 
of  Lepidoptera  caused  by  exposure  of  the  pupse  to  different  tem- 
perature conditions.     Trans.  Ent.  Soc.  London,  pp.   155-168,  pi.  9. 

Urech,  F.  1891.  Beobachtungen  iiber  die  verschiedenen  Schuppenfarben 
und  die  zeitliche  Succession  ihres  Auftretens  (Farbenfelderung) 
auf  den  Puppenfliigelchen  von  Vanessa  urticse  und  lo.  Zool. 
Anz.,  jhg.  14,  pp.  466-473- 

Beddard,  F.  E.  1892.  Animal  Coloration.  8 -f  288  pp.,  4  pis.,  36  figs. 
London,  Swan  Sonnenschein  &  Co.     New  York,  Macmillan  &  Co. 

Gould,  L.  J.  1892.  Experiments  in  1890  and  1891  on  the  colour-relation 
between  certain  lepidoptcrous  larvfe  and  their  surroundings,  to- 
gether with  some  other  observations  on  lepidoptcrous  larvae. 
Trans.  Ent.  Soc.  London,  pp.  215-246,  pi.  11. 

Merrifield,  F.  1892.  The  effects  of  artificial  temperature  on  the  colouring 
of  several  species  of  Lepidoptera,  with  an  account  of  some  experi- 
ments on  the  effects  of  light.     Trans.  Ent.  Soc.  London,  pp.  33-44. 


44^  ENTOMOLOGY 

Poulton,  E.  B.  1892.  Further  experiments  upon  the  colour-relation  be- 
tween certain  lepidopterous  larvce.  pupje,  cocoons  and  imagines 
and  their  surroundings.  Trans.  Ent.  Soc.  London,  pp.  293-487, 
pis.  14,  15. 

Urech,  F.  1892.  Beobachtungen  iiber  die  zeitliche  Succession  der  Auf- 
tretens  der  Farbenfelder  auf  den  Puppenfliigelchen  von  Pieris 
brassicas.     Zool.  Anz.,  jhg.   15,  pp.  284-290,  293-299. 

Urech,  F.  1892.  Ueber  Eigenschaften  der  Schuppenpigmente  einiger 
Lepidopteren-Species.     Zool.  Anz.,  jhg.   15,  pp.  299-306. 

Weismann,  A.  1892,  1898.  The  Germ-Plasm.  Trans,  by  W.  N.  Parker 
and  H.  Ronnfeldt.  See  pp.  399-409.  on  climatic  variation  in 
butterflies. 

Dixey,  F.  A.  1893.  On  the  phjdogenetic  significance  of  the  variations 
produced  by  difference  of  temperature  in  Vanessa  atalanta. 
Trans.  Ent.  Soc.  London,  pp.  69-73. 

Merrifield,  F.  1893.  The  effects  of  temperature  in  the  pupal  stage  on  the 
colouring  of  Pieris  napi,  Vanessa  atalanta,  Chrysophanus  phloeas. 
and  Ephyra  punctaria.     Trans.  Ent.  Soc.  London,  pp.  55-67,  pi.  4. 

Poulton,  E.  B.  1893.  The  Experimental  Proof  that  the  Colours  of  certain 
Lepidopterous  Larvse  are  largely  due  to  modified  plant  Pigments 
derived  from  Food.  Proc.  Roy.  Soc.  London,  vol.  54.  pp.  417- 
430,  pis.  3,  4. 

Urech,  F.  1893.  Beitrage  zur  Kenntniss  der  Farbe  von  Insektenschuppen. 
Zeits.  wiss.  Zool.,  bd.  57,  pp.  306-384. 

Bateson,  W.  1894.  Materials  for  the  Study  of  Variation  treated  with 
especial  Regard  to  Discontinuity  in  the  Origin  of  Species.  16  -j- 
598  pp.,  209  figs.     London  and  New  York.     Macmillan  &  Co. 

Dixey,  F.  A.  1894.  Mr.  Merrifield's  Experiments  in  Temperature- Varia- 
tion as  bearing  on  Theories  of  Heredity.  Trans.  Ent.  Soc.  Lon- 
don, pp.  439-446. 

Hopkins,  F.  G.  1894.  The  Pigments  of  the  Pieridas.  Proc.  Roy.  Soc. 
London,  vol.  57,  pp.  5-6. 

Kellogg,  V.  L.  1894.  The  Taxonomic  Value  of  the  Scales  of  the  Lepidop- 
tera.     Kansas  Univ.  Quart.,  vol.  3,  pp.  45-89,  pis.  9,  10,  figs.  1-17. 

Merrifield,  F.  1894.  Temperature  Experiments  in  1893  on  several  species 
of  Vanessa  and  other  Lepidoptera.  Trans.  Ent.  Soc.  London,  pp. 
425-438,  pi.  9. 

Hopkins,  F.  G.  1895.  The  Pigments  of  the  Pieridse:  A  Contribution  to 
the  Study  of  Excretory  Substances  which  function  in  Ornament. 
Phil.  Trans.  Roy.  Soc.  London,  vol.  186,  pp.  661-682. 

Spuler,  A.  1895.  Beitrag  zur  Kenntniss  des  feineren  Baues  und  der  Phy- 
logenie  der  Fliigelbedeckung  der  Schmetterlinge.  Zool.  Jahrb., 
Abth.  Anat.  Ont.,  bd.  8,  pp.  520-543,  taf.  36. 

■Standfuss,  M.  1895.  On  the  Causes  of  Variation  and  Aberration  in  the 
Lnago  Stage  of  Butterflies,  with  Suggestions  on  the  Establishment 
of  New  Species.  Trans,  by  F.  A.  Dixey.  Entomologist,  vol.  28, 
pp.  69-76,  102-114,  142-150. 


LITERATURE  449 

Mayer,  A.  G.  1896.  The  Development  of  the  Wing  Scales  and  their  Pig- 
ment in  Butterflies  and  iSIoths.  Bull.  Mus.  Comp.  Zool.,  vol.  29, 
pp.  209-236,  pis.   1-7. 

Weismann,  A,  1896.  New  Experiments  on  the  Seasonal  Dimorphism  of 
Lepidoptera.  Trans,  by  W.  E.  Nicholson.  The  luitomologist, 
vol.  29,  pp.  29-39,  etc. 

Brunner  von  Wattenwyl,  C.  1897.  Betrachtungen  iiber  die  Farbenpracht 
der  Insekten.  16  pp.,  9  taf.  Leipzig.  Trans,  by  E.  J.  Bles : 
Observations  on  the  Coloration  of  Insects.     16  pp.,  9  pis.     Leipsic. 

Fischer,  E.  1897-99.  Bcitriige  zur  e.xpcrimentellen  Lepidopterologie. 
illustr.  Zeits.  Ent.,  1x1.  2-4.  12  taf. 

Mayer,  A.  G.  1897.  On  the  Color  and  Color-Patterns  of  Moths  and 
Butterflies.  Proc.  Bost.  Soc.  Nat.  Hist.,  vol.  27,  pp.  243-330,  pis. 
i-io.     Also  Bull.  jNIus.  Comp.  Zool.,  vol.  30,  pp.  169-256,  pis.  i-io. 

Von  Linden,  Grafin  M,  1898.  Untersuchungen  iiber  die  Entwicklung  der 
Zeichnung  des  Schmetterlingsfliigels  in  der  Puppe.  Zeits.  wiss. 
Zool,  bd.  65,  pp.   1-49,  taf.   1-3. 

Newbigin,  M.  I.  1898.  Colour  in  Nature.  12 -(-344  PP-  London.  John 
Alurray.* 

Von  Linden,  Grafin  M.  1899.  Untersuchungen  iiber  die  Entwickelung  der 
Zeichnung  der  Schmetterlingsfliigels  in  der  Puppe.  lUustr.  Zeits. 
Ent.,  bd.  4,  pp.  19-22. 

Urech,  F.  1899.  Einige  Bemerkungen  zum  zeitlichen  Auftreten  der 
Schuppen-Pigmentstofife  von  Pieris  brassicae.  Illustr.  Zeits.  Ent., 
bd.  4,  pp.  51-53. 

Von  Linden,  la  Comtesse  M.  1902.  Le  dessin  des  ailes  des  Lepidopteres. 
Recherches  sur  son  evolution  dans  I'ontogenese  et  la  phylogenese 
des  especes,  son  origine  et  sa  valeur  systematique.  Ann.  Sc.  nat. 
Zool.,  ser.  8,  t.   14,  pp.  1-196,  pis.   1-20. 

Weismann,  A.  1902.  Vortriige  iiber  Descendenztheorie.  2  vols.  12 -\- 
456  pp.,  95  figs.;  6 -|- 462  pp.,  3  pis.,  36  figs.  Jena.  G.  Fischer. 
See  pp.  65-102. 

Von  Linden,  Grafin  M.  1903.  Morphologische  und  physiologisch-chemische 
Untersuchungen  iiber  die  Pigmente  der  Lepidopteren.  i.  Die 
gelben  imd  roten  Farbstofife  der  Vanessen.  Archiv  ges.  Phys.,  bd. 
98,  pp.  1-89,  I  taf.,  3  figs. 

Poulton,  E,  B.  1903.  Experiments  in  1893,  1894  and  1896  upon  the  col- 
our-relation between  lepidopterous  larvae  and  their  surroundings, 
and  especially  the  efifect  of  lichen-covered  bark  upon  Odontopera 
bidentata,  Gastropacha  quercifolia,  etc.  Trans.  Ent.  Soc.  London, 
pp.  311-374.  pis.   16-18. 

Tower,  W.  L.  1903.  The  Development  of  the  Colors  and  Color  Patterns 
of  Coleoptera,  with  Observations  upon  the  Development  of  Color 
in  other  Orders  of  Insects.  Univ.  Chicago  Decenn.  Publ.,  vol.  10, 
pp.  1-40,  pis.  1-3. 

30 


450  ENTOMOLOGY 

Vernon,    H.    M.      1903.      Variation    in    Animals    and    Plants.      9-1-415   pp. 

New  York.     Henry  Holt  &  Co. 
Enteman,    W.    M.      1904.      Coloration    in    Polistes.      Publ.    Carnegie    Inst. 

Washington,  no.  ig,  88  pp.,  6  pis.,  26  figs.* 
Von  Linden,  Grafin  M.     1905.     Physiologische  Untersuchungen  an  Schmet- 

terlingen.     Zeits.  wiss.   Zool.,  bd.  82,  pp.  411-444,  taf.  25.* 

ADAPTIVE    COLORATION 
Bates,   H.   W.     1862.     Contributions   to    an    Insect   Fauna   of  the   Amazon 

Valley.     Lepidoptera :    Heliconidje.     Trans.   Linn.    Soc.    Zool.,   vol. 

23,  PP-  495-566,  pis.  55,  56. 
Wallace,  A.   R.      1867.      [Theory   of  Warning   Coloration.]      Trans.    Ent. 

Soc.  London,  ser.  3,  vol.  5,  Proc,  pp.  80-81. 
Butler,  A.   G.     1869.     Remarks   upon   certain   Caterpillars,   etc.,   which   are 

unpalatable  to  their  enemies.     Trans.  Ent.  Soc.  London,  pp.  27-29. 
Trimen,  R.     1869.     On  some  remarkable  Mimetic  Analogies  among  Afri- 
can Butterflies.     Trans.  Linn.  Soc.  Zool.,  vol.  26,  pp.  497-522,  pis. 

42.  43- 
Meldola,   R.     1873.     On   a   certain   Class   of   Cases   of   Variable   Protective 

Colouring  in  Insects.     Proc.  Zool.  Soc.  London,  pp.   153-162. 
Miiller,  F.     1879.     Ituna  and  Thyridia ;   a  remarkable  case  of  Mimicry  in 

Butterflies.     Trans.,  R.  Meldola,  Proc.  Ent.  Soc.  London,  pp.  20- 

29,  figs.  1-4. 
Blackiston,    T.,    and    Alexander,    T.      1884.      Protection    by    Mimicry — A 

Problem  in   Mathematical  Zoology.     Nature,  vol.  29,  pp.  405-406. 
Poulton,  E.  B.     1884.     Notes  upon  or  suggested  by  the  Colours,  Markings 

and    Protective    Attitudes    of    certain    Lepidopterous    Larvje    and 

Pupae,  and  of  a  phytophagous  hymenopterous  larva.     Trans.  Ent. 

Soc.  London,  pp.  27-60,  pi.  i. 
Poulton,  E.  B.     1885.     Further  notes  upon  the  markings  and  attitudes  of 

lepidopterous  larvae.     Trans.  Ent.  Soc.  London,  pp.  281-329,  pi.  7. 
Poulton,  E.  B.     1887.     The   Experimental   Proof  of  the   Protective   Value 

of  Colour  and  Markings  in  Insects  in  reference  to  their  Vertebrate 

Enemies.     Proc.  Zool.  Soc.  London,  pp.  191-274. 
Wallace,  A.  R.      1889.      Darwinism.      16  -f  494  PP,  Zl  figs.      London   and 

New  York.     Macmillan  &  Co. 
Poulton,   E.   B.     1890.     The   Colours   of   Animals.     13  -|-  360  pp.,    i   pL,   66 

figs.     New  York.     D.   Appleton  &  Co. 
Beddard,  F.  E.      1892.      Animal  Coloration.      8-I-288  pp.,  4  pis.,  36  figs. 

London,  Swan  Sonnenschein  &  Co.     New  York,  Macmillan  &  Co. 
Haase,  E.     1893.     Untersuchungen  iiber  die  Mimicry  auf  Grundlage  eines 

natiirlichen  Systems  der  Papilioniden.     Bibl.   Zool.,  Heft  8,  Theil 

I,  120  pp.,  6  taf.;  Theil  2,  161  pp.,  8  taf.     Trans.  Theil  2,  C.  M. 

Child,  Stuttgart,  1896,  154  pp.,  8  pis. 
Finn,  F.     1895-97.     Contributions  to  the  Theory  of  Warning  Colours  and 

Mimicry.     Journ.  Asiat.  Soc.  Bengal,  vols.  64-67. 
Dixey,  F.  A.     1896.     On  the  Relation  of  Mimetic  Patterns  to  the  Original 

Form.       Trans.   Ent.  Soc.  London,  pp.  65-79,  pls.  3-5^ 


LITERATURE  45 1 

Piepers,  M.  C.  1896.  Miinetisme.  Cong.  Intern.  Zool,  3  Sess.,  Leyden, 
pp.  460-476. 

Dixey,  F.  A.  1897.  iMimctic  Attraction.  Trans.  Ent.  Soc.  London,  pp. 
,1' 7-33 1,  pl-  7- 

Mayer,  A.  G.  1897.  On  the  Color  and  Color-Patterns  of  Moths  and 
Butterflies.  Proc.  Best.  Soc.  Nat.  Hist.,  vol.  27,  pp.  243-330,  pis. 
i-io.     Also  Bull.  Mus.  Comp.  Zool.,  vol.  30,  pp.  169-256,  pis.  i-io.* 

Trimen,  R.  1897.  Mimicry  in  Insects.  Proc.  Ent.  Soc.  London,  pp.  74- 
97.* 

Webster,  F.  M.  1897.  Warning  Colors,  Protective  Mimicry  and  Protec- 
tive Coloration.  27tli.  Ann.  Rept.  Ent.  Soc.  Ontario  (1896),  pp. 
80-86,  figs.  80-82. 

Newbigin,  M.  I.  1898.  Colour  in  Nature.  12 -(-344  pp.  London.  John 
Murray.* 

Poulton,  E.  B.  1898.  Natural  Selection  the  Cause  of  Mimetic  Resem- 
blance and  Conmion  Warning  Colors.  Journ.  Linn.  Soc.  Zool., 
vol.  26,  pp.  558-612,  pis.  40-44,  figs.   1-7. 

Judd,  S.  D.  1899.  The  Efficiency  of  Some  Protective  Adaptations  in 
Securing  Insects  from  Birds.     Amer.  Nat.,  vol.  33,  pp.  461-484. 

Marshall,  G.  A.  K.,  and  Poulton,  E.  B.  1902.  Five  Years'  Observations 
and  Experiments  (1896-1901)  on  the  Bionomics  of  South  African 
Insects,  chiefly  directed  to  the  Investigation  of  Mimicry  and 
Warning  Colours.  Trans.  Ent.  Soc.  London,  pp.  287-584,  pis. 
9-^3- 

Shelford,  R.  1902.  Observations  on  some  Mimetic  Insects  and  Spiders 
from  Borneo  and  Singapore.  Proc.  Zool.  Soc.  London,  1902,  vol. 
2,  pp.  230-284,  pis.  19-23. 

Weismann,  A.  1902.  Vortrage  iiber  Descendenztheorie.  2  vols.  12  -f 
456  pp.,  95  figs. ;  6  +  462  pp.,  3  pis.,  36  figs.  Jena.  G.  Fischer. 
See  pp.  103-133. 

Piepers,  M.  C.  1903.  Mimikry,  Selektion  und  Darwinismus.  452  pp. 
Leiden.     E.  J.  Brill. 

Poulton,  E.  B.  1903,  Experiments  in  1893,  1894  and  1896  upon  the  colour- 
relation  betvi^een  lepidopterous  larvae  and  their  surroundings,  and 
especially  the  effect  of  lichen-covered  bark  upon  Odontopera 
bidentata,  Gastropacha  quercifolia,  etc.  Trans.  Ent.  Soc.  London, 
PP-  311-374,  pis.   16-18. 

Packard,  A.  S.  1904.  The  Origin  of  the  ^Markings  of  Organisms  (Poecilo- 
genesis)  due  to  the  Physical  rather  than  to  the  Biological  Envi- 
ronment ;  with  Criticisms  of  the  Bates-Miiller  Hypothesis.  Proc. 
Amer.  Phil.  Soc,  vol.  43,  pp.  393-450.* 

ORIGIN    OF    ADAPTATIONS    AND    OF    SPECIES 

Darwin,  C.  1859,  1869.  The  Origin  of  Species  by  means  of  Natural 
Selection.  11 -j- 440  pp.  London.  New  York.  D.  Appleton  & 
Co. 


452  ENTOMOLOGY 

Spencer,  H.     1866-67.     The  Principles  of  Biology.     2  vols.     16  +  1041  pp., 

306  figs.     New  York.     D.  Appleton  &  Co. 
Wallace,  A.  R.     1870.     Contributions  to  the  Theory  of  Natural  Selection. 

16-1-384  pp.     London  and  New  York.     Macmillan  &  Co. 
Weismann,  A.      1880-81.      Studies  in  the  Theory  of  Descent.      Trans,  by 

R.  Meldola.     554  pp.,  8  pis.     London. 
Cope,  E.   D.     1887.     The  Origin  of  the   Fittest.     19  +  467  pp.,   18  pis.,  81 

figs.     New  York.     D.  Appleton  &  Co. 
Henslow,  G.     1888.     The  Origin  of  Floral  Structures  through   Insect  and 

other  Agencies.     19  -|-  349  pp.,  88  figs.     New  York.     D.  Appleton 

&  Co. 
Wallace,  A.  R.      1889.      Darwinism.      16 -{-494  pp.,  ^7  figs.      London  and 

New  York.     Macmillan  &  Co. 
Eimer,  G.  H.  T.     1890.     Organic  Evolution  as  the  Result  of  the  Inheritance 

of  Acquired  Characters  according  to  the  Laws  of  Organic  Growth. 

Trans,    by   J.    T.    Cunningham.     28  -|-  435   pp.     London    and    New 

York.     Macmillan  &  Co. 
Weismann,  A.     1891,  1892.     Essays  upon  Heredity  and  Kindred  Biological 

Problems.     Ed.  by  E.  B.  Poulton,  S.  Schonland  and  A.  E.  Ship- 
ley.    Vol.    I,    15 -(-471    pp.;   vol.   2,  8-I-226  pp.     Ed.   2.     Oxford. 

Clarendon  Press. 
Romanes,  G.  J.      1892,   1897,   1901.      Darwin  and  After  Darwin.      Vol.   i. 

The  Darwinian  Theory,   14 4-460  pp.,  125  figs.;  vol.  2,  Heredity 

and  Utility,  10  -|-  344  pp.,  4  figs. ;  vol.  3,  Isolation  and  Physiological 

Selection,  8-|-i8i  pp.     Chicago.     Open  Court  Pub.  Co. 
Weismann,  A.      1892,   1898.      The   Germ-Plasm.      A   Theory  of   Heredity. 

Trans,  by  W.  N.  Parker  and  H.  Ronnfeldt.     22  -|-  477  pp.,  24  figs. 

New  York.     C.  Scribner's  Sons. 
Romanes,    G.   J.     1893.     An    Examination    of    Weismannism.     9  -|-  221    pp. 

Chicago.     Open  Court  Pub.  Co. 
Bateson,   W.     1894.     Materials   for   the   Study  of  Variation   treated   with 

especial  Regard  to  Discontinuity  in  the  Origin  of  Species.     16  -}- 

598  pp.,  209  figs.     London  and  New  York.     Macmillan  &  Co. 
Baldwin,  J.  M.     1895.     Consciousness  and   Evolution.     Science,  vol.   2    (n. 

s.),  pp.  219-223. 
Delage,  Y.     1895.     La  structure  du  protoplasma  et  les  theories  sur  I'here- 

dite  et  les  grands  problemes  de  la  biologie  generale.     16  -f  878  pp. 

Paris.     C.  Reinwald  et  Cie.* 
Baldwin,  J.  M.     1896.     Physical  and  Social  Heredity.     Amer.  Nat.,  vol.  30, 

pp.  422-428. 
Baldwin,  J.  M.     1896.     A  New  Factor  in  Evolution.     Amer.  Nat.,  vol.  30, 

pp.  441-451-  536-553- 
Baldwin,  J.  M.     1896.     Heredity  and  Instinct.     Science,  vol.  3   (n.  s.),  pp. 

438-441,  558-561. 
Cope,  E.  D.     1896.     The  Primary  Factors  of  Organic  Evolution.     16  +  547 

pp.,  120  figs.     Chicago.     Open  Court  Pub.  Co. 
Morgan,  C.  Lloyd.     1896.     On  Modification  and  Variation.     Science,  vol.  4 

(n.  s.),  pp.  733-740. 


LITERATURE  453 

Morgan,  C.  Lloyd.     1896.     ir;il)it  and  Instinct.     351   pp.     London  and  New 

York.     v..  Arnold. 
Osborn,  H.  F.     1896.     Ontoscnic  and    Plixlogcnic  Variation.     Science,  vol. 

4   (n.  s.),  pp.  786-789, 
Bailey,   L.    H.     1896,    1897.     The    Survival   of   the    Unlike.     515   pp.     New 

York  and  London.     The  Macmillan  Co. 
Baldwin,  J.   M.      1897.      Organic    Selection.      Science,   vol.    5    (n.    s.),   pp. 

634-6;.(i. 
De  Vries,  H.      1901-3.      l^ie   Mutalionstheorie.      14  +  752  pp..    12  pis.,    159 

figs.     Leipzig.     Veit  &   Co.* 
Baldwin,   J.   M.     1902.     Development   and   Evolution.     16 -{-395   pp.     New 

York  and  London.     The  Macmillan  Co. 
Weismann,  A.     1902.     Vortriige  iiber  Descendenztheorie.     Bd.   i,   12 -j- 456 

pp.,  95  figs.;  bd.  2,  6  +  462  pp.,  36  figs.,  3  taf.     Jena.     G.  Fischer. 
Morgan,   T.   H.      1903.      Evolution   and   Adaptation.      13  +  470  pp.,   5   figs. 

New  York  and  London.     The  ALacmillan  Co. 
Vernon,    H.    M.      1903.      Variation    in    Animals    and    Plants.      9  +  415    pp. 

New  York.     Henry  Holt  &  Co. 
Kellogg,   V.   L.,   and   Bell,   R.   G.     1904.     Studies   of   Variation    in    Lisects. 

Proc.  Wash.  Acad.  Sc,  vol.  6,  pp.  203-332,  figs.  1-81. 
Metcalf,  M.  M.     1904.     An  Outline  of  the  Theory  of  Organic  Evolution. 

22  +  204   pp.,    loi    pis.,   46   figs.      New    York    and    London.      The 

■\Lacmillan  Co.* 
Weismann,  A.     1904.     The  Evolution  Theory.     Trans,  by  J.   A.   Thomson 

and  ^I.  R.  Thomson.     2  vols.     16  +  821  pp.,  131  figs.     London.     E. 

Arnold. 
De   Vries,   H.      1905.      Species   and   Varieties :     their   Origin   by   Mutation. 

Ed.   by   D.   T.    MacDougal.     18  +  847   pp.     Chicago.     Open    Court 

Pub.  Co. 
Gulick,   J.   T.      1905.      Evolution,   Racial   and    Habitudinal.      12+  269  pp. 

Carnegie  Inst.  Washington. 
Reid,    G.    A.     1906.     The    Principles    of    Heredity.     Ed.    2.     13  +  379    pp. 

London.     Chapman  &  Hall,  Ltd. 

INSECTS    IN   RELATION    TO    PLANTS 

Darwin,  C.  1877.  The  Eflfects  of  Cross  and  Self  Fertilisation  in  the  Vege- 
talile  Kingdom.     8  +  482  pp.     New  York.     D.   Appleton  &  Co. 

Lubbock,  J.  1882.  On  British  Wild  Flowers  considered  in  Relation  to 
Insects.  Ed.  4.  16+186  pp.,  130  figs.  London.  Macmillan  & 
Co. 

Mijller,  H.  1883.  The  Fertilisation  of  Flowers.  12  +  669  PP-i  1S6  figs. 
London.     ^Macmillan  &  Co. 

Darwin,  C.  1884.  The  Various  Contrivances  by  which  Orchids  are  fer- 
tilised by  Insects.  Ed.  2.  16  +  300  pp.,  38  figs.  New  York.  D. 
Appleton  &  Co. 

Darwin,  C.  1884.  Insectivorous  Plants.  10  +  462  pp.,  30  figs.  New 
York.     D.  Appleton  &  Co. 


454  ENTOMOLOGY 

Cheshire,  F.  R.  1886.  Bees  and  Bee-keeping.  2  vols.  Vol.  i,  7  +  336 
pp.,  71  figs.,  8  pis.;  vol.  2,  652  pp..  127  figs.,  I  pi.  London.  L. 
Upcott  Gill. 

Forbes,  S.  A.  1886.  Studies  on  the  Contagious  Diseases  of  Insects.  Bull. 
111.  St.  Lab.  Nat.  Hist.,  vol.  2,  pp.  257-321,  i  pi. 

Thaxter,  R.  1888.  The  Entomophthorese  of  the  United  States.  Mem. 
Bost.  Soc.  Nat.  Hist.,  vol.  4.  pp.  133-201,  pis.  14-21. 

Robertson,  C.  1889-99.  Flowers  and  Insects.  I-XIX.  Bot.  Gaz.,  vols. 
14-22,  25,  28. 

Seitz,  A.  1890,  1893,  1894.  Allgemeine  Biologic  der  Schmetterlinge. 
Zool.  Jahrb.,  Abth.  Syst.,  etc.,  bd.  5,  pp.  281-343;  bd.  7,  pp.  131- 
186,  823-851.* 

Eckstein,  K.  1891.  Pflanzengallen  und  Gallentiere  88  pp.,  4  taf.  Leip- 
zig.    R.  Freese. 

Robertson,  C.  1891-96.  Flowers  and  Insects.  Trans.  Acad.  Sc,  St. 
Louis,  vols.  5-7. 

Cooke,  M.  C.  1892.  Vegetable  Wasps  and  Plant  Worms.  5  -)-  364  pp.,  4 
pis.,  51   figs.     London. 

Riley,  C.  V.  1892.  Some  Interrelations  of  Plants  and  Insects.  Proc. 
Biol.  Soc.  Wash.,  vol.  7,  pp.  81-104,  figs.  1-15. 

Riley,  C.  V.  1892.  The  Yucca  Moth  and  Yucca  Pollination.  Third  Ann. 
Rept.  Mo.  Bot.  Garden,  pp.  99-158,  pis.  34-43. 

Moller,  A.  1893.  Die  Pilzgarten  einiger  siidamericanischer  Ameisen. 
Bot.  Mitt,  aus  den  Tropen,  heft  6.  7-I-127  pp.,  7  taf.,  4  figs. 
Jena.     G.  Fischer. 

Trelease,  W.  1893.  Further  Studies  of  Yuccas  and  their  Pollination. 
Fourth  Ann.  Rept.  Mo.  Bot.  Garden,  pp.  181-226,  pis.  1-23. 

Adler,  H.,  and  Straton,  C,  R.  1894.  Alternating  Generations.  A  Biolo- 
gical Study  of  Oak  Galls  and  Gall  F"lies.  40  -j-  198  pp.,  3  pis. 
Oxford.     Clarendon  Press."** . 

Webster,  F.  M.  1894.  Vegetal  Parasitism  among  Insects.  Journ.  Colum- 
bus Hort.  Soc,  pp.  1-19,  pis.  3-5,  figs.  I,  2. 

Heim,  F.  L.  1898.  The  Biologic  Relations  between  Plants  and  Ants. 
Ann.  Rept.  Smiths.  Inst.  1896,  pp.  411-455,  pis.  17-22.  Trans. 
from  Compt.  rend.  24me  Sess.  Ass.  fr.  I'av.  Sc.  1895,  pp.  31-75. 

Schimper,  A.  F.  W.  1898.  Pflanzen-Geographie  auf  physiologischer 
Grundlage.  18  -|-  876  pp.,  502  figs.,  5  plates,  4  maps.  Jena.  G. 
Fischer.  (See  pp.  147-170.)*  Trans:  1903.  W.  R.  Fisher. 
Plant-Geography  upon  a  Physiological  Basis.  30-4-839  pp.,  502 
figs.,  4  maps.     Oxford,  Clarendon  Press.     (See  pp.   126-156.)* 

Benton,  F.  1899.  The  Honey  Bee:  A  Manual  of  Instruction  in  Apicul- 
ture. Bull.  LT.  S.  Dept.  Agric,  Div.  Ent.,  no.  i  (n.  s.),  pp.  1-118, 
pis.  i-ii,  figs.  1-76.* 

Needham,  J.  G.  1900.  The  Fruiting  of  the  Blue  Flag  (Iris  versicolor  L.). 
Amer.  Nat.,  vol.  34,  pp.  361-386,  pi.  i,  figs.  1-4. 

Gibson,  W.  H.  1901.  Blossom  Hosts  and  Insect  Guests.  19  +  197  pp., 
figs.     New  York.     Newson  &  Co. 


LITERATURE 


455 


Connold,  E.  T.     1902.     British  Vegetable  Galls.     12  +  312  pp.,   130  pis.,  10 

figs.     New  York.     E.  P.  Button  &  Co. 
Cook,  M.  T.      1902-04.      Galls  and  Insects  Producing  Them.      Pts.  I-IX. 

Ohio  Nat.,  vols.  2-4,  pis.     Same,  Bull.  Ohio  St.  Univ.,  ser.  6,  no. 

15;  ser.  7.  no.  20;  ser.  8,  no.  13. 
Needham,  J.  G.     1903.     Button-Bush  Insects.     Psyche,  vol.  10,  pp.  22-31. 
Cowan,  T.  W.     1904.     The  Honey  Bee:  its  Natural  History,  Anatomy  and 

Physiology.     ]*2d.  2.     12  +  220  pp..  Jt,  figs.     London.     Iloulston  & 

Sons.* 
Rossig,  H.     1904.     Von  welchen  Organen   der  Gallwespenlarven  geht  der 

Reiz    zur    Bildung    der    Pflanzengalle    aus?      Zool.    Jahrb.,    Abth. 

Syst.,  etc.,  bd.  20,  pp.  19-90,  taf.  3-6.* 

INSECTS    IN    RELATION    TO    OTHER    ANIMALS 


Aughey,   S.      1878.      Notes   on   the   Nature   of   the   Food   of   the   Birds   of 

Nebraska.     First  Rept.  U.  S.  Ent.  Cpmni.,  Appendix,  2,  pp.  13-62. 
Forbes,  S.  A.     1878.     The  Food  of  Illinois  Fishes.     Bull.  111.  St.  Lab.  Nat. 

Hist.,  vol.  I,  no.  2,  pp.  71-89. 
Forbes,  S.  A.     1880.     The  Food  of  Birds.     Trans.  111.  St.  Hort.  Soc,  vol. 

13  (1879),  pp.  120-172. 
Forbes,  S.  A.     1880.     On  Some  Interactions  of  Organisms.     Bull.   III.   St. 

Lab.  Nat.  Hist.,  vol.  i,  no.  3,  pp.  3-17. 
Forbes,  S.  A.     ijBBo.    The  Food  of  Fishes,     Bull.  III.  St.  Lab.  Nat.  Hist., 

vol.  I,  no.  3,  pp.  18-65. 
Forbes,  S.  A.     1880.     On  the  Food  of  Young  Fishes.     Bull.  111.   St.  Lab. 

Nat.  Hist.,  vol.  i,  no.  3,  pp.  66-79. 
Forbes,  S.  A.     1880.     The  Food  of  Birds.     Bull.  111.   St.  Lab.   Nat.   Hist., 

vol.  I,  no.  3,  pp.  80-148. 
Forbes,  S.  A.     1883.     The  Regulative  Action  of  Birds  upon  Insect  Oscilla- 
tions.    Bull.  111.  St.  Lab.  Nat.  Hist.,  vol.  i,  no.  6,  pp.  2i-2,^- 
Forbes,  S.  A.     1883.    The  Food  of  the  Smaller  Fresh-Water  Fishes.     Bull. 

111.  St.  Lab.  Nat.  Hist.,  vol.  i,  no.  6.  pp.  65-94. 
Forbes,  S.  A.     1883.     The  First  Food  of  the  Common  White-Fish.     Bull. 

III.  St.  Lab.  Nat.  Hist.,  vol.  i,  no.  6,  pp.  95-109. 
Dimmock,  G.     1886.     Belostomidse  and  some  other  Fish-destroying  Bugs. 

Ann.  Rept.  Fish  Game  Comm.  Mass.,  pp.  67-74,  i  fig.* 
Forbes,  S.  A.     1888.     Studies  on  the  Food  of  Fresh-Water  Fishes.     Bull. 

111.  St.  Lab.  Nat.  Hist.,  vol.  2.  pp.  433-473- 
Forbes,  S.  A.     1888.     On  the   Food  Relations  of  Fresh-Water  Fishes :   a 

Summary  and   Discussion.     Bull.   111.   St.   Lab.   Nat.   Hist.,  vol.   2, 

PP-  475-538. 
Wilcox,  E.  V.     1892.     The  Food  of  the  Robin.     Bull.  Ohio  Agr.  Exp.  Sta., 

no.  43,  pp.  115-131- 
Beal,  F.  E.  L.     1897.     Some  Common  Birds  in  their  Relation  to  Agricul- 
ture.    Farmer's   Bull.   U.   S.    Dept.    Agric,   no.   54,  pp.    1-40,  figs. 

1-22 


45^  ENTOMOLOGY 

Kirkland,   A.   H.     1897.     The    Habits,   Food    and    Economic   Value   of   the 

American  Toad.     Bull.  Hatch  Exp.  Sta.  Mass.  Agr.  Coll.,  no.  46, 

pp.  3-30,  pl.  2. 
Judd,    S.    D.     1899.     The    Efficiency    of    Some    Protective    Adaptations    in 

Securing  Insects  from  Birds.     Amer.  Nat.,  vol.  33,  pp.  461-484. 
Palmer,    T.    S.     1900.     A    Review    of    Economic    Ornithology.     Yearbook 

U.  S.  Dept.  Agric.  1899,  pp.  259-292. 
Judd,  S.  D.     1901.     The  Food  of  Nestling  Birds.     Yearbook  U.  S.   Dept. 

Agric.  1900,  pp.  411-436,  pis.  49-53.  figs.  48-56. 
Forbes,   S.  A.     1903.     Studies  of  the   Food   of   Birds,   Insects   and   Fishes. 

Second  Ed.     Bull.  111.  St.  Lab.  Nat.  Hist.,  vol.  i,  no.  3. 
Weed,  C.  M.,  and  Dearborn,  N.     1903.     Birds  in  their  Relations  to  Man. 

8-I-380   pp.,    figs.      Philadelphia    and    London.      J.    B.    Lippincott 

Co.* 

INSECTS    IN    RELATION    TO    DISEASES 

Blandford,  W.  F.  H.  1896.  Jhe  Tsetse  fly-disease.  Nature,  vol.  53,  pp. 
566-568,  figs.   I,  2. 

Sternberg,  G.  M.  1897.  The  Alalarial  Parasite  and  other  Pathogenic 
Protozoa.     Pop.  Sc.  Mon.,  vol.  50,  pp.  628-641,  figs.   1-3. 

Kanthack,  A.  A.,  Durham,  H.  E.,  and  Blandford,  W.  F.  H.  1898.  On 
Nagana,  or  Tsetse  fly  disease.  Proc.  Roy.  Soc.  Lond.,  vol.  64, 
pp.  1 00-118. 

Finlay,  C.  J.  1899.  Mosquitoes  considered  as  Transmitters  of  Yellow 
Fever  and  Malaria.     Psyche,  vol.  8,  pp.  379-384. 

Nuttall,  G.  H.  F.  1899.  On  the  role  of  Insects,  Arachnids  and  Myriapods, 
as  carriers  in  the  spread  of  Bacterial  and  Parasitic  Diseases  of 
Man  and  Animals.  A  Critical  and  Historical  Study.  Johns 
Hopk.  Hosp.  Rept,  vol.  8,  no.  i,  154  pp.,  3  pis. 

Ross,  R.  1899.  Life-History  of  the  Parasites  of  Malaria.  Nature,  vol. 
60,  pp.  322-324. 

Christy,  C.  1900.  Mosquitos  and  Malaria  :  a  summary  of  knowledge  on 
the  subject  up  to  date;  with  an  account  of  the  natural  history  of 
mosquitos.     9  -|-  80  pp.,  5  pis.     London. 

Howard,  L.  0.  1900.  Notes  on  the  Mosquitoes  of  the  United  States:  giv- 
ing some  account  of  their  structure  and  biology,  with  remarks  on 
remedies.  Bull.  U.  S.  Dept.  Agric,  Div.  Ent.,  no.  25  (n.  s.),  70 
pp.,  22  figs. 

Howard,  L.  0.  1900.  A  contribution  to  the  study  of  the  insect  fauna  of 
human  excrement  (with  especial  reference  to  the  spread  of  typhoid 
fever  by  flies).  Proc.  Wash.  Acad.  Sc,  vol.  2,  pp.  541-604,  pis. 
30,  31,  figs.  17-38- 

Ross,  R.     1900.     Malaria  and  Mosquitoes.     Nature,  vol.  61,  pp.  522-527. 

Ross,  R.,  and  Fielding-Ould,  R.  1900.  Diagrams  illustrating  the  Life- 
history  of  the  Parasites  of  Malaria.  Quart.  Journ.  Micr.  Sc,  vol. 
43   (n.  s.),  pp.  571-579,  pis.  30,  31- 

Grassi,  B.  1901.  Die  Malaria-Studien  eines  Zoologen.  8 -{-250  pp.,  8 
taf.     Jena.     G.  Fischer. 


LITERATURE  457 

Howard,  L.  0.  1901.  AFosquitocs;  how  tliey  live;  how  they  carry  disease; 
how  they  are  chissitied ;  how  they  may  be  destroyed.  15 -|- 241 
pp.,  50  tigs.,  I  pi.     New  York.     McChire,  Philhps  &  Co. 

Sternberg,  G.  M.  1901.  Tlie  Transmission  of  Yellow  l-Y'ver  ])y  Mos- 
quitoes.    Pop.  So.  IMon.,  vol.  59,  pp.  225-241. 

Howard,  L.  0.  1902.  Insects  as  Carriers  and  Spreaders  of  Disease.  Year- 
hook  V.  S.  Dept.  Agric.  1901,  pp.  177-192,  figs.  5-20. 

Braun,  M.  1903.  Die  thierischen  Parasiten  des  Menschen.  Rev.  Ed. 
12 +  360  pp.,  272  figs.     Wiirzburg. 

Sternberg,  G.  M.  1903.  Infection  and  Immunity;  with  special  Reference 
to  the  Prevention  of  Infectious  Diseases.  5  +  293  pp.,  12  figs. 
New  York  and  London.     G.  P.  Putnam's  Sons. 

Blanchard,  R.  1905.  Les  Moustiques,  histoire  naturelle  et  medicale. 
673  pp.,  316  figs.     Paris.     De  Rudeval. 

INTERRELATIONS    OF    INSECTS 

Van   Beneden,   P.   J.     1876.     Animal    Parasites    and    Messmates.     28  +  274 

pp..  83  figs.     New  York.     D.  Appleton  &  Co. 
McCook,    H.    C.      1877.      Mound-making    Ants    of    the    Alleghenies,    their 

Architecture  and  Habits.     Trans.  Amer.  Ent.  Soc,  vol.  6,  pp.  253- 

296,  figs.   1-13. 
Fabre,  J.  H.     1879-1905.     Souvenirs  entomologiques.     fetudes  sur  I'instinct 

et    les    moeurs    des    insectes.      9    Series.      Paris.      C.    Delagrave. 

Trans,  of  Sen  I:   1901.     Fabre,  J.  H.     Insect  Life.     12 +  320  pp., 

16  pis.     London  and  New  York.     The  Macmillan  Co. 
Forbes,  S.  A.      1880.      Notes  on  Insectivorous  Coleoptera.      Bull.   111.   St. 

Lab.  Nat.  Hist.,  vol.  i,  no.  3,  pp.  153-160.     Second  Ed.,  1903. 
McCook,   H.   C.     1880.     The    Natural   History  of  the   Agricultural   Ant   of 

Texas.     310  pp..  24  pis.     Philadelphia.     J.  B.  Lippincott  &  Co. 
Webster,  F.  M.     1880.     Notes  upon  the  Food  of  Predaceous  Beetles.     Bull. 

111.   St.   Lab.   Nat.   Hist.,   vol.    i.   no.   3.  pp.    149-152.     Second   Ed., 

1903. 
McCook,  H.  C.     1881.     Note  on  a  new  Northern  Cutting  Ant.  Atta  septen- 

trionalis.     Proc.  Acad.  Nat.  Sc.  Phila.  1880,  pp.  359-363,  i  fig. 
McCook,  H.  C.     1881.     The  Shining  Slavemaker.     Notes  on  the  Architec- 
ture  and   Habits   of  the   American   Slave-making  Ant.    Polyergus 

lucidus.     Proc.  Acad.  Nat.  Sc.  Phila.  1880,  pp.  376-384.  pi.  19. 
Lubbock,  J.     1882,  1901,  1904.     Ants,  Bees  and  Wasps.     19 -|- 448  pp.,  31 

figs.,  5  pis.     New  York.     D.  Appleton  &  Co. 
McCook,  H.  C.     1882.     The  Honey  Ants  of  the  Garden  of  the  Gods,  and 

the    Occident    Ants    of    the    American    Plains.     188    pp.,    13    pis. 

Philadelphia.     J.  B.  Lippincott  &  Co. 
Forbes,  S.  A.     1883.    The  Food  Relations  of  the  Carabidas  and  Coccinel- 

lidse.     Bull.  111.  St.  Lab.  Nat.  Hist.,  vol.  i,  no.  6,  pp.  33-64. 
Cheshire,  F.  R.      1886.      Bees  and  Bee-keeping.      2  vols.      Vol.   1,74-  336 

pp.,  8  pis.,  71  figs. ;  vol.  2,  652  pp.,  127  figs.,  I  pi.      London.      L. 

Upcott  Gill. 


45°  ENTOMOLOGY 

Seitz,    A.      1890,    1893,    1894.      AUgemeine    Biologic    der    Schmetterlinge. 

Zool.  Jahrb.,  Abth.  Svst.,  etc.,  bd.  5,  pp.  281-343;   bd.  7,  pp.   131- 

186,  823-851.* 
Verhoeff,  C.     1892.     Beitrage  zur  Biologic  der  Hymenoptera.     Zool.  Jahrb., 

Abth.  Syst.,  etc.,  bd.  6,  pp.  680-754,  taf.  30,  31. 
Wasmann,  E.     1894.     Kritisches  Verzeichnis  der  myrmekophilen  und  ter- 

mitophilen  Arthropoden.     231  pp.     Berlin.     F.  L.  Dames. 
Grassi,  B.,  and  Sandias,  A.     1896-97.    The  Constitution  and  Development 

of  the  Society  of  Termites,  etc.     Trans,  by  W.  F.  H.  Blandford. 

Quart.  Journ.   Micr.   Sc,  vol.  39,  pp.  245-322,  pis.   16-20;  vol.  40, 

PP-  1-75- 
Janet,  C.     1896.     Les  Fourmis.     Bull.  Soc.  zool.  France,  vol.  21,  pp.  60-93. 

Sep.,  37  pp.,  Paris. 
Howard,  L.   0.     1897.     A   Study  in   Insect   Parasitism.     Bull.   U.    S.   Dept. 

Agric,  Div.  Ent.,  tech.  ser.  no.  5,  pp.  1-57,  figs.  1-24. 
Peckham,   G.  W.,  and  E.  G.     1898.     On  the   Instincts  and  Habits  of  the 

Solitary  Wasps.     Bull.  Wis.  Geol.  Nat.  Hist.  Surv.,  no.  2,  sc.  ser. 

no.   I,  4  +  245  pp.,   14  pis. 
Wasmann,    E.      1898.      Die    Gaste    der    Ameisen    und    Termiten.      lUustr. ' 

Zeits.  Ent.,  bd.  3,  i  taf. 
Benton,  F.     1899.     The  Honey  Bee  :    A  Manual  of  Instruction  in  Apicul- 
ture.    Bull.  U.  S.  Dept.  Agric,  Div.  Ent.,  no.  i    (n.  s.),  pp.  1-118, 

pis.   i-ii,  figs.   1-76.* 
Fielde,  A.  M.     1901.     A   Study  of  an  Ant.     Proc.  Acad.  Nat.   Sc.   Phila., 

vol.  52,  pp.  425-449- 
Fielde,  A.  M.      1901.      Further  Study  of  an  Ant.     Proc.   Acad.   Nat.   Sc. 

Phila.,  vol.  53,  pp.  521-544- 
Wheeler,  W.   M.     igoi.     The    Compound   and    jNIixed    Nests   of   American 

Ants.     Amer.  Nat.,  vol.  35,  pp.  431,  513,  701,  791,  figs.  1-20. 
Enteman,  M.  M.     1902.     Some  Observations  on  the  Behavior  of  the  Social 

Wasps.     Pop.  Sc.  Mon.,  vol.  61,  pp.  339-351. 
Fielde,  A.  M.     1902.     Notes  on  an  Ant.     Proc.  Acad.  Nat.  Sc.  Phila.,  vol. 

54,  pp.  599-625. 
Dickel,   F.      1903.      Die   Ursachen  der  geschlechtlichen   Diflferenzirung   im 

Bienenstaat.     Archiv  ges.  Phys.,  bd.  95,  pp.  66-106,  fig.  i. 
Fielde,  A.  M.     1903.     Supplementary  Notes  on  an  Ant.     Proc.  Acad.  Nat. 

Sc.   Phila.,  vol.  55,  pp.  491-495- 
Heath,  H.     1903.     The  Habits  of  California  Termites.     Biol.   Bull.,  vol.  4, 

pp.  47-63,  figs.   1-3. 
Janet,   C.      1903.      Observations   sur   les   guepes.      85   pp.,   30  figs.      Paris. 

C.  Naud. 
Melander,   A.   L.,   and   Brues,   C.   T.     1903.     Guests   and    Parasites   of   the 

Burrowing  Bee  Halictus.     Biol.  Bull.,  vol.  5,  pp.   1-27,  figs.  1-7. 
Fielde,  A.  M.     1904.     Power  of  Recognition  among  Ants.     Biol.  Bull.,  vol. 

7,  pp.   227-250,  4  figs. 
Fielde,  A.  M.,  and  Parker,  G.  H.     1904.     The  Reactions  of  Ants  to  Material 

Vibrations.     Proc.  Acad.  Nat.  Sc.   Phila.,  vol.  56,  pp.  642-650.* 


LITERATURE  459 

Wheeler,  W.  M.     1904.     A   New   Type  of   Social   Parasitism   among  Ants. 
Bull.  Anier.  JNIus.  Nat.  Hist.,  vol.  jo,  pp.  347-375- 

INSECT   BEHAVIOR 

Pouchet,   G.     1872.     De   I'influence    de   la   lumiere   sur   les   larves   de   dip- 

leres  privees  d'organes  exterieurs  de  la  vision.     Rev.   Mag.  Zool., 

scr.  2,  t.  23,  pp.  110-117,  etc.,  pis.  12-16. 
Fabre,  J.  H.     1879-1905.     Souvenirs  entomologiques.     fitudes  sur  I'instinci 

et    les    moeurs    des    insectes.      9    Series.      Paris.      C.    Delagrave. 

Trans,  of  Ser.  I:    1901.     Fabre,  J.  H.     Insect  Life.     12 -(-320  pp., 

16  pis.     London  and  New  York.     The  Macmillan  Co. 
Lubbock,  J.     1882,  1884.     Ants,  Bees  and  Wasps.     19  +  448  pp.,  31   ligs.,  5 

pis.     New  York.     D.  Appleton  &  Co. 
Graber,  V.     1884.     Grundlinien  zur  Erforschung  des  Helligkeits-  und  Far- 

bensinnes  der  Tiere.     8  -|-  322  pp.     Prag  und  Leipzig. 
Romanes,  G.  J.      1884.      Animal   Intelligence.      14  -|-  520  pp.      New  York. 

D.  Appleton  &  Co. 
Lubbock,  J.     1888.     On  the  Senses,  Instincts  and  Intelligence  of  Animals, 

with   Special  Reference   to   Insects.     294-292  pp.,    118  figs.     New 

York.     D.  Appleton  &  Co. 
Plateau,  F.     1889.     Recherches  experimentales  sur  la  Vision  chez  les  Ar- 

thropodes.     Mem.  cour.  Acad.  roy.  Belgique,  t.  43,  pp.   1-91. 
Eimer,  G.  H.  T.     1890.     Organic  Evolution  as  the  Result  of  the  Inheritance 

of  Accjuired  Characters  according  to  the  Laws  of  Organic  Growth. 

28  -\-  435    pp.     Trans,    by   J.    T.    Cunningham.     London   and    New 

York.     Macmillan  &  Co. 
Loeb,  J.     1890.     Der  Heliotropismus  der  Thiere  und   seine  Uebereinstim- 

mung  mit  dem  Heliotropismus  der  Pflanzen.     118  pp.     Wiirzburg. 
Seitz,   A.     1890.     Allgemeine    Biologic   der    Schmetterlinge.     Zool.    Jahrb., 

Abth.  Syst.,  bd.  5,  pp.  281-343. 
Exner,  S.     1891.     Die  Physiologic  der  facettirten  Augen  von  Krebsen  und 

Insecten.     8  +  206  pp.,  8  taf.,  23  figs.     Leipzig  und  Wien. 
Loeb,  J.     1 891.     Ueber   Geotropismus   hei   Thieren.     Arch.   ges.    Phys.,   bd. 

49,  pp.   175-189,  figs. 
Morgan,  C.  Lloyd.     1891.     Animal  Life  and  Intelligence.     13 -|- 512  pp.,  40 

figs.     Boston.     Ginn  &  Co. 
James,  W.     1893.     The   Principles  of  Psychology.     2  vols.     18  +  1393  pp., 

94  figs.     New  York.     Henry  Holt  &  Co. 
Loeb,    J.      1893.      Ueber    kunstliche    Umwandlung    positiv    heliotropischer 

Thiere  in  negativ  heliotropische  und  umgekehrt.     Arch.  ges.  Phys., 

bd.  54,  pp.  81-107. 
Baldwin,  J.  M.     1896.     Heredity  and  Instinct.     Science,  vol.  3   (n.  s.),  pp. 

438-441,  558-561. 
Morgan,  C.  Lloyd.     1896.     Habit  and  Instinct.     351  pp.     London  and  New 

York.     E.  Arnold. 
Davenport,    C.    B.     1897,    1899.     Experimental    [Morphology.     2    Pts.     32-)- 

508  pp.,   140  figs.     New  York  and  London.     The  Macmillan  Co. 


460  ENTOMOLOGY 

Loeb,  J.     1897.     Zur  Theorie  der  physiologischen  Licht-  mid  Schwerkraft- 

wirkungcn.     Arch.  ges.   Phys..  l)d.  64.  pp.  439-466. 
Bethe,  A.     i8g8.     Diirfen  wir  den  Ameisen  und   Bienen  psychische  Quali- 

taten  zuschreiben?     Archiv  ges.  Phvs.,  bd.  70,  pp.  15-100,  taf.  i,  2, 

5  figs. 
Peckham,  G.  W.,   and  E.   G.     1898.     On   the   Instincts   and   Habits   of  the 

Solitary   Wasps.     Bull.    Wis.    Geol.    Nat.    Hist.    Surv.,   no.    2,    sc. 

ser.  no.  1.4  +  245  pp.,  14  pis. 
Verworn,   M.     1899.     General   Physiolog>'.     An   Outline   of  the   Science   of 

Life.     Trans,  by  F.   S.  Lee.     16  +  615  pp.,  285  figs.     London  and 

New  York.     IMacmillan  &  Co. 
Wasmann,  E.     1899.     Die  psj'chischen  Fahigkeiten  der  Ameisen.     Zoolog- 

ica,  heft  26,  6  +  132  pp.,  3  taf.     Stuttgart.     E.  Nagele. 
Wheeler,    W.    M.     1899.     Anemotropism   and    Other   Tropisms    in    Insects. 

Arch.  Entw.  Org.,  bd.  8,  pp.  373-381. 
Whitman,  C.  0.     1899.     Animal  Behavior.     Biol.  Lect.,  Marine  Biol.  Lab., 

Wood's  Holl,  Mass.,  1898,  pp.  285-338.     Boston.     Ginn  &  Co. 
Loeb,  J.     1900.     Comparative   Physiology   of  the   Brain   and   Comparative 

Psychology.     309  pp.,  39  figs.     New  York,  G.   P.   Putnam's  Sons. 

London,  J.  Murray.* 
Morgan,  C.  Lloyd.     1900.     Animal  Behaviour.     8  +  344  pp.,  26  figs.     Lon- 
don.    E.  Arnold. 
Radl,  E.      1901.      Ueber  den   Phototropismus  einiger  Arthropoden.      Biol. 

Centralb.,  bd.  21,  pp.  75-86. 
Radl,    E.      1901.      L'^ntersuchungen    iiber   die   Lichtreactionen    der   Arthro- 
poden.    Arch.  ges.  Phys.,  bd.  87,  pp.  418-466. 
Enteman,  M.  M.     1902.     Some  Observations  on  the  Behavior  of  the  Social 

Wasps.     Pop.  Sc.  Mon.,  vol.  61,  pp.  339-351. 
Weismann,  A.      1902.      Vortrage  iiber  Descendenztheorie.      2  vols.      12 -f 

456  pp.,  95  figs.;  6  +  462  pp.,  3  pis.,  36  figs.     Jena.     G.   Fischer. 

See  pp.  159-181. 
Kathariner,  L.      1903.      Versuche   iiber  die   Art   der   Orientierung  bei   der 

Honigbienc.     Biol.  Centralb.,  bd.  23,  pp.  646-660,   i   fig. 
Kellogg,  V.  L.     1903.     Some  Insect  Reflexes.     Science,  vol.  18   (n.  s.),  pp. 

693-696. 
Morgan,    T.    H.     1903.     Evolution    and    Adaptation.     134-470   pp.,    5    figs. 

New  York  and  London.     The   ■Nlacmillan  Co. 
Parker,  G.  H.     1903.     The   Phototropism  of  the  ]\Iourning-cloak  Butterfly, 

Vanessa  antiopa  Linn.     Mark  Anniv.  Vol.,  pp.  453-469,  pi.  33.* 
Fielde,  A.  M.,  and  Parker,  G.  H.     1904.     The  Reactions  of  Ants  to  Material 

Vibrations.     Proc.  Acad.  Nat.  Sc.  Phila.,  vol.  56,  pp.  642-650.* 
Forel,  A.     1904.     The  Psychical  Faculties  of  Ants  and  some  other  Insects. 

Ann.   Rept.    Smiths.    Inst.    1903,   pp.   587-599.     Trans,    from    Proc. 

Fifth  Intern.  Zool.  Congr.  Berlin,  1901,  pp.   141-169. 
Jennings,    H.    S.     1904.     Contributions   to   the    Study   of   the    Behavior   of 

Lower  Organisms.     256  pp.,  81  figs.     Carnegie  Inst.  Washington.* 


LITERATURE  46 I 

Carpenter,  F.  W.     1905.     Tlic  Reactions  of  the   Pomace   Fly    (Drosophila 

ampelophila   Loew)    to   Light,   Gravity,   and    ^Mechanical    Stinnila- 

tion.     Anier.   Nat.,  vol.  39,  pp.   157-171.* 
Hartman,  C.     1905.     Ohservations  on  the   Habits  of  some  Solitary  Wasps 

of  Texas.     I'ull.  Univ.  "i'c.xas,  no.  65,  sc.  ser.  no.  7,  pp.  1-73,  4  pis. 
Holmes,  S.  J.     1905.     The  Reactions  of  Ranatra  to  Light.     Jonrn.   Comp. 

Neur,   Psych.,  vol.   15,  pp.  305-349,  figs.   1-6. 
Loeb,  J.     1905.     Studies  in  General  Physiology.     2  vols.     24  -f-  782  pp.,  162 

figs.     L^niv.  Chicago  Decenn.  Pnbl.,  ser.  2,  vol.   15,  pts.  i,  2. 
Wasmann,  E.     1905.     Comparative  Studies  in  the  Psychology  of  Ants  and 

of    Higher   Animals.     10  +  200  pp.     St.    Louis    and   Freiburg,    B. 

Herder;  London  and  Edinburgh,  Sands  &  Co.* 


GEOGRAPFHCAL    DISTRIBUTION 

Darwin,  C.  1859,  1869.  On  the  Origin  of  Species  by  means  of  Natural 
Selection.  Pp.  1 1  -\-  440.  New  York.  D.  Appleton  &  Co.  See 
pp.  302-357. 

LeConte,  J.  L.  1859.  The  Coleoptera  of  Kansas  and  Eastern  New  Mex- 
ico.    Smithson.  Contrib.,  vol.  11,  6  +  58  pp.,  2  pis.,  map. 

Bates,  H.  W.  1864.  The  Naturalist  on  the  River  Amazons.  12 -|- 466 
pp.,  figs.     London.     J.   Murray. 

Wallace,  A.  R.  1865.  On  the  Phenomena  of  Variation  and  Geographical 
Distribution  as  illustrated  by  the  Papilionidas  of  the  Malayan  Re- 
gion.    Trans.  Linn.  Soc.  ZooL,  vol.  25,  pp.   1-71,  pis.  1-8. 

Wallace,  A.  R.  1869.  The  Malay  Archipelago.  12 -{-638  pp.,  51  figs.,  10 
maps.     New  York.     Harper  &  Bros. 

Murray,  A.  1873.  On  the  Geographical  Relations  of  the  Chief  Coleop- 
terous Faunas.     Journ.  Linn.  Soc.  ZooL,  vol.  11,  pp.  1-89. 

Belt,  T.  1874,  1888.  The  Naturalist  in  Nicaragua.  32  +  403  pp.,  figs. 
London.     J.  Murray;  E.  Bumpus. 

Wallace,  A.  R.  1876.  The  Geographical  Distribution  of  Animals.  2  vols. 
Vol.  I,  214-503  pp.,  13  pis.,  5  maps;  vol.  2,  8 -(- 607  pp.,  7  pis,,  2 
maps.     New   York.     Harper  &   Bros. 

Semper,  K.  1881.  Animal  Life  as  affected  by  the  Natural  Conditions  of 
Existence.  16  -f  472  pp.,  106  figs.,  2  maps.  New  York.  D.  Apple- 
ton  &  Co. 

Wallace,  A.  R.  1881.  Island  Life,  or  the  Phenomena  and  Causes  of  Insu- 
lar Faunas  and  Floras,  etc.  16  -|-  522  pp.,  26  maps  and  figs.  New 
York.     Harper  &  Bros. 

Gill,  T.  1884.  The  Principles  of  Zoogeography.  Proc.  Biol.  Soc.  Wash., 
vol.  2,  pp.   1-39. 

Forbes,  H.  0.  1885.  A  Naturalist's  Wanderings  in  the  Eastern  Archi- 
pelago. 19  +  536  pp.,  figs.,  pis.,  maps.  New  York.  Harper  & 
Bros. 


462  ENTOMOLOGY 

Schwarz,   E.   A.     1888.     The   Insect   Fauna   of   Semitropical   Florida,   with 

Special   Regard   to   the   Coleoptera.     Ent.   Amer.,   vol.   4,   pp.    165- 

175- 
Merriam,  C.  H.     1890.     Results  of  a  Biological  Survey  of  the   San  Fran- 
cisco Mountain  Region  and  Desert  of  the  Little  Colorado,  Arizona. 

U.    S.    Dept.    Agric,   Div.    Ornith.    Mamm.,    N.    A.    Fauna,   no.   3, 

6  +  136  pp.,  13  pis.,  5  maps,  2  figs. 
Schwarz,  E.  A.     1890.     On  the  Coleoptera  common  to  North  America  and 

other  Countries.     Proc.  Ent.  Soc.  Wash.,  vol.  i,  pp.   182-194. 
Seitz,    A.      1890,    1893,    1894.      Allgemeine    Biologic    der    Schmetterlinge. 

Zool.  Jahrb.,  Abth.  Syst.,  etc.,  bd.  5,  pp.  281-343;  bd.  7,  pp.   131- 

186,  823-851.* 
Trouessart,   E.   L.      1890.      La    Geographie    Zoologique.      11 -{-338   pp.,   63 

figs.,  2  maps.     Paris. 
Wallace,  A.  R.     1890.     A.   Narrative  of  Travels  on  the  Amazon   and  Rio 

Negro,  etc.     Ed.  3.     14  -|-  ^63  pp.,  16  pis.     London,  New  York  and 

Melbourne.     Ward,  Lock  &  Co. 
Packard,   A.   S.     1891.     The  Labrador   Coast.     513   pp.,   figs.     New   York. 

N.  D.  C.  Hodges. 
Bates,   H,   W.      1892.      The   Naturalist  on   the   River   Amazons.      Reprint. 

89  +  395  PP-.  figs.     London.     J.  ]Murray. 
Distant,  W.  L.     1892.     A  Naturalist  in  the  Transvaal.     16 -\- 277  pp.,  pis., 

figs.     London.     R.  H.  Porter. 
Hudson,  W.   H.      1892.      The   Naturalist   in   La    Plata.      8 -(-388  pp.,   figs. 

London.     Chapman  &  Hall. 
Webster,  F.   M.      1892.      Modern   Geographical   Distribution   of   Insects   in 

Indiana.     Proc.  Ind.  Acad.   Sc,  pp.  81-88,  map. 
Merriam,    C.    H.      1893.      The    Geographic    Distribution   of   Life    in    North 

America,    with    special    Reference    to    the    Mammalia.      Smithson. 

Rept.    1891,   pp.    365-415.     From    Proc.    Biol.    Soc.    Wash.,   vol.   7, 

pp.  1-64. 
Elwes,  H.  J.     1894.     The  Geographical  Distribution  of  Butterflies.     Trans. 

Ent.  Soc.  London,  Proc,  pp.. 52-84. 
Hamilton,  J.     1894.     Catalogue  of  the  Coleoptera  common  to  North  Amer- 
ica, Northern  Asia  and  Europe,  with  Distribution  and  Bibliogra- 
phy.    Trans.  Amer.  Ent.  Soc,  vol.  21,  pp.  345-416 -|- 19. 
Merriam,  C.  H.     1894.     Laws  of  Temperature   Control  of  the  Geographic 

Distribution    of    Terrestrial    Animals    and    Plants.      Nat.    Geogr. 

Mag.,  vol.  6,  pp.  229-238,  3  maps. 
Scudder,  S.  H.     1894.     The  Effect  of  Glaciation  and  of  the  Glacial  Period 

on  the  Present  Fauna  of  North  America.     Amer.  Journ.  Sc,  ser. 

3,  vol.  48,  pp.   179-187- 
Webster,  F.  M.     1894.     Some  Insect  Immigrants  in  Ohio.     Bull.  Ohio  Agr. 

Exp.  Sta.,  ser.  2,  vol.  6.  no.  51   (1893),  pp.  1 18-129,  figs.  17,  18. 
Whymper,  E.   1894.     Travels  amongst  the   Great  Andes  of  the   Equator. 

24 -f  456  pp.,  20  pis.,  4  maps,  118  figs.     New  York.     C.  Scribner's 

Sons.     1891.     Suppl.    Appendix.     22 -|- 147    pp.,    figs.     London.     J. 

Murray. 


LITERATURE  463 

Beddard,  F.  E.  1895.  A  Text-book  of  Zoogeograpliy.  84-246  pp.,  5 
maps.     Cambridge,  Eng.     University  Press. 

Howard,  L.  0.  1895.  Notes  on  the  Geographical  Distribution  within  the 
United  States  of  certain  Insects  injuring  CuUivated  Crops.  Proc. 
Ent.  Soc.  Wash.,  vol.  3,  pp.  219-226. 

Webster,  F.  M.  1895.  Notes  on  the  Distrilxition  of  some  Injurious  In- 
sects.    Proc.   Ent.  Soc.  Wash.,  vol.  3,  pp.  284-290. 

Webster,  F.  M.  1896.  The  Probable  Origin  and  Difltusion  of  Blissus 
leucopterus  and  Murgantia  histrionica.  Journ.  Cine.  Soc.  Nat. 
Hist.,  vol.  18,  pp.  141-155.  fig-  I.  Pl-  5- 

Carpenter,  G.  H.  1897.  The  Geographical  Distribution  of  Dragon-ilies. 
Proc.  Roy.  Dublin  Soc,  vol.  8,  pp.  439-468,  pi.  17. 

Heilprin,  A.  1897.  The  Geographical  and  Geological  Distribution  of  Ani- 
mals.    12-)- 435  pp.,  map.     New  York.     D.  Appleton  &  Co. 

Saville-Kent,  W.  1897.  The  Naturalist  in  Australia.  15  +  302  pp.,  50 
pis.,   104  figs.     London.     Chapman  «&  Hall. 

Webster,  F.  M.  1897.  Biological  Effects  of  Civilization  on  the  Insect 
Fauna  of  Ohio.  Fifth  Ann.  Kept.  Ohio  St.  Acad.  Sc,  pp.  32-46, 
2  figs. 

Merriam,  C.  H.  1898.  Life  Zones  and  Crop  Zones  of  the  United  States. 
Bull.  U.  S.  Dept.  Agric,  Div.  Biol.  Surv.,  no.  10,  pp.  1-79,  map. 

Webster,  F.  M.  1898.  The  Chinch  Bug.  Bull.  U.  S.  Dept.  Agric,  Div. 
Ent.,  no.   15   (n.  s.),  82  pp.,   19  figs.      (See  pp.  66-82.) 

Semon,  R.  1899.  In  the  Australian  Bush  and  on  the  Coast  of  the  Coral 
Sea,  etc.  15  +  55^  pp.,  4  maps,  86  figs.  London  and  New  York. 
Macmillan  &  Co. 

Tower,  W.  L.  1900.  On  the  Origin  and  Distribution  of  Leptinotarsa 
decem-lineata  Say,  and  the  Part  that  some  of  the  Climatic  Fac- 
tors have  played  in  its  Dissemination.  Proc.  Amer.  Ass.  Adv. 
Sc,  vol.  49,  pp.  225-227. 

Adams,  C.  C.  1902.  Postglacial  Origin  and  Migrations  of  the  Life  of  the 
Northeastern  United  States.  Journ.  Geogr.,  vol.  i,  pp.  303-310, 
352-357,  map. 

Adams,  C.  C.  1902.  Southeastern  United  States  as  a  Center  of  Geograph- 
ical Distribution  of  Flora  and  Fauna.  Biol.  Bull.,  vol.  3,  pp.  115- 
131.* 

Tutt,  J.  W.  1902.  The  Migration  and  Dispersal  of  Insects.  132  pp. 
London.     E.  Stock. 

Webster,  F.  M.  1902.  The  Trend  of  Insect  Diffusion  in  North  America. 
32d.  Ann.  Rept.  Ent.   Soc.  Ontario   (1901),  pp.  63-67,  maps  1-3. 

Webster,  F.  M.  1902.  Winds  and  Storms  as  Agents  in  the  Diffusion  of 
Insects.     Amer.  Nat.,  vol.  36,  pp.  795-801. 

Webster,  F.  M.  1903.  The  Diffusion  of  Insects  in  North  America. 
Psyche,  vol.  10,  pp.  47-58,  pi.  2. 

Jacobi,  A.     1904.     Tiergeographie.     152  pp.,  2  maps.     Leipzig. 


464  ENTOMOLOGY 


GEOLOGICAL    DISTRIBUTION 

Herr,  0.  1847-53.  Die  Insectenfauna  der  Tertiargebilde  von  Qiningen 
und  von  Radoboj  in  Croatien.  3  Th.  644  pp.,  40  taf.  Leipzig. 
From  Neue  Denks.  scliweiz.  Gesell.  Naturw.,  bd.  8,  11,  13. 

Scudder,  S.  H.  1880.  The  Devonian  Insects  of  New  Brunswick.  Ann. 
^lem.  Bost.  Soc.  Nat.  Hist.,  41  pp.,  i  pi. 

Scudder,  S.  H.  1882.  A  Bibliography  of  Fossil  Insects.  Bibl.  Contrib. 
Lilir.  Harv.  Univ.,  no.   13.     47  pp.     Cambridge,  ISIass.* 

Scudder,  S.  H.  1885.  The  Earliest  Winged  Insects  of  America :  a  Re- 
examination of  the  Devonian  Insects  of  New  Brunswick,  etc.  8 
pp.,  I  pi.,  2  figs.     Cambridge,  Mass. 

Scudder,  S.  H.  1885.  Systematische  Uebersicht  der  fossilen  Myriopoden, 
Arachnoideen  und  Insekten.  In  K.  A.  Zittel :  Handbuch  der 
Palseontologie,  abth.  i,  bd.  2,  pp.  721-831,  figs.  894-1109.  Trans. 
1900.  C.  R.  Eastman.  Text-Book  of  Palaeontology,  vol.  i,  pp. 
682-691,  figs.  1441-1476.  London  and  New  York.  Macmillan  & 
Co.* 

Scudder,  S.  H.  1886.  The  Cockroach  of  the  Past.  In  L.  C.  Miall  and 
A.  Denny.  The  Structure  and  Life-History  of  the  Cockroach,  pp. 
205-220,  figs.  1 19-125.     London  and  Leeds.* 

Scudder,  S.  H.  1886.  Systematic  Review  of  our  Present  Knowledge  of 
Fossil  Insects.  Bull.  U.  S.  Geol.  Surv.,  no.  31,  128  pp.  Wash- 
ington. 

Scudder,  S.  H.  1889.  The  Fossil  Butterflies  of  Florissant.  Eighth  Ann. 
Rept.  Dir.  L'.  S.  Geol.  Surv.,  pp.  433-474,  pi.  53.     Washington. 

Scudder,  S.  H.  i8go.  The  Work  of  a  Decade  upon  Fossil  Insects. 
Psyche,  vol.   5,  pp.   287-295. 

Scudder,  S.  H.  1890.  A  Classed  and  Annotated  Bibliography  of  Fossil 
Insects.     Bull.  U.  S.  Geol.  Surv.,  no.  69,  loi  pp.     Washington.* 

Scudder,  S.  H.  1890.  The  Tertiary  Insects  of  North  America.  U.  S. 
Geol.  Surv.  Terr.,  vol.  13,  734  pp.,  28  pis.,  i  map,  3  figs.  Wash- 
ington. 

Scudder,  S.  H.  1891.  Index  to  the  Known  Fossil  Insects  of  the  World, 
including  Myriapods  and  Arachnids.  Bull.  LI.  S.  Geol.  Surv.,  no. 
71,  744  pp.     Washington.* 

Scudder,  S.  H.  1892.  Some  Insects  of  Special  Interest  from  Florissant. 
Colorado,  and  other  Points  in  the  Territories  of  Colorado  and 
Utah.     Bull.  U.  S.  Geol.  Surv.,  no.  93.  35  pp.,  3  pis.     Washington. 

Scudder,  S.  H.  1893.  Insect  Fauna  of  the  Rhode  Island  Coal  Field.  Bull. 
LI.  S.  Geol.  Surv.,  no.  loi,  27  pp.,  2  pis.     Washington. 

Scudder,  S.  H.  1893.  The  American  Tertiary  Aphidre,  with  a  List  of  the 
Known  Species  and  Tables  for  their  Determination.  Thirteenth 
Ann.  Rept.  U.  S.  Geol.  Surv.,  pt.  2,  pp.  341-372,  pis.  102-106. 
^^^'lshington. 

Scudder,  S.  H.  1893.  Tertiary  Rhynchophorous  Coleoptera  of  the  LInited 
States.  Monogr.  U.  S.  Geol.  Surv..  vol.  21,  ii-|-2o6  pp.,  12  pis. 
Washington. 


LITERATURE  465 

Brongniart,  C.  1894.  Rechcrches  pour  servir  a  I'histoire  des  inscctes  fos- 
siles  des  temps  primaires,  etc.  2  vols.  537  pp.,  37  pis.  St. 
fitienne. 

Scudder,  S.  H.  1894.  Tertiary  Tipulidse,  with  Special  Reference  to  those 
of  Florissant,  Colorado.  Proc.  Amer.  Phil.  Soc,  vol.  32,  83  pp.,  9 
pis. 

Scudder,  S.  H.  1896.  Revision  of  the  American  Fossil  Cockroaches,  with 
Descriptions  of  New  Forms.  Bull.  U.  S.  Geol.  Surv.,  no.  124,  176 
pp.,  12  pis.     Washington. 

Goss,  H.  1900.  The  Geological  Antiquit}'  of  Insects.  Ed.  2.  4  +  5^  PP- 
London.     Ciurney  &  Jackson.* 

Scudder,  S.  H.  igoo.  Adephagous  and  Clavicorn  Colcoptera  from  the 
Tertiary  Deposits  at  Florissant,  Colorado,  etc.  Monogr.  U.  S. 
Geol.  Surv.,  vol.  40,  148  pp.,  11  pis.     Washington. 

Scudder,  S.  H.  1900.  Canadian  Fossil  Insects.  4.  Additions  to  the  Cole- 
opterous Fauna  of  the  Interglacial  Clays  of  the  Toronto  District, 
etc.  Contrib.  Can.  Pal,  Geol.  Surv.  Can.,  vol.  2,  pp.  67-92,  pis. 
6-15.     Ottawa. 


INSECTS    IN    RELATION    TO    MAN 

Harris,  T.  W.  1862.  A  Treatise  on  Some  of  the  Insects  Injurious  to 
Vegetation.     Third  Ed.     11  +640  pp.,  278  figs.,  8  pis.     Boston. 

Lintner,  J.  A.  1882.  Importance  of  Entomological  Stud}-,  etc.  First 
Ann.  Rept.  Inj.  Ins.,  pp.  1-80,  hgs.  1-12. 

Saunders,  W.  1883.  Insects  Injurious  to  Fruits.  436  pp.,  440  figs. 
Philadelphia.     J.   B.  Lippincott  &  Co. 

Henshaw,  S.,  and  Banks,  N.  1 889-1 901.  Bibliography  of  the  more  im- 
portant Contributions  to  American  Economic  Entomology.  8  pts. 
1318  pp.     Washington.* 

Packard,  A.  S.  1889.  Guide  to  the  Study  of  Insects.  Ed.  9.  12  +  715 
pp.,  668  figs.,  15  pis.     New  York.     Henry  Holt  &  Co. 

Howard,  L.  0.  1894.  A  Brief  Account  of  the  Rise  and  Present  Condition 
of  Ofificial  Economic  Entomology.    -Insect  Life,  vol.  7,  pp.  55-107. 

Sempers,  F.  W.  1894.  Injurious  Insects  and  the  Use  of  Insecticides. 
10  -j-  216  pp.,  I  pL,   184  figs.     Philadelphia.     W.  A.   Burpee  &  Co. 

Smith,  J.  B.  1896.  Economic  Entomology  for  the  Farmer  and  Fruit- 
Grower,  etc.  Pp.  12+11-481,  483  figs.  Philadelphia.  J.  B. 
Lippincott  Co. 

Howard,  L.  0.  1899.  The  Economic  Status  of  Insects  as  a  Class.  Sci- 
ence, vol.  9   (n.  s.),  pp.  233-247. 

Theobald,  F.  V.  1899.  A  Text-Book  of  Agricultural  Zoology.  17-1-511 
pp.,  225  figs.     Edinburgh  and  London.     Wm.  Blackwood  &  Sons. 

Howard,  L.  0.     1900.     Progress  in  Economic  Entomology  in  the  United 
States.     Yearbook  V.  S.  Dept.  Agric,  1899,  pp.  135-156.  pi.  3. 
31 


466  ENTOMOLOGY 

Sanderson,  E.  D.  1902.  Insects  Injurious  to  Staple  Crops.  10  +  295 
pp.,  163  figs.  New  York.  John  Wiley  &  Sons. 
Most  of  the  literature  on  the  economic  entomology  of  the  United  States 
is  contained  in  the  following  works :  Reports  U.  S.  Ent.  Comm. ;  Repts. 
Govt.  Entomologists;  Bulletins  U.  S.  Dept.  Agric,  Div.  Ent;  Insect  Life; 
Reports  and  Bulletins  by  the  several  State  Entomologists ;  Bulletins  of  the 
various  Experiment  Stations. 


NDEX 


An  asterisk   *   denotes   an   illustration. 


Abdomen,  65  ;  appendages  of,  *67. 
*i5o,  *i52;  extremity,  68;  moditica- 
tions,  66  ;  segments,  65 

Acacia,  *272,  272 

Accessory  glands,  *i40,  *i4i,  *i42 

Achonites,  *9,  10 

Acquired  characters,  243 

Acridiida?,  *io,  11  :  moults  of,  165; 
spiracles,  66 

Acridiiiiii,  27;  respiratory  muscles  of, 
*I39 

Aculeata,  21 

Adams,  on  dispersal,  383 

Adaptations,  of  larv?e,  165  ;  of  legs,  51, 
*53  ;  of  mandibles,  37,  *38  ;  origin 
of,  237  ;  protective,  297 

Adaptive  coloration,  216;  classifica- 
tion, 234  :  evolution,  236  ;  variation, 
241 

Adelung,  von,  428 

Adler,  418,  454 

Adventitious  resemblance,  219 

Ageronia,  104 

Aggressive  resemblance,  235 

As-rionidK,  caudal  gills  of,  *i34 

Air-sacs,  133 

Alary  muscles,  *i25 

Albinism,  201 

Alexander,  450 

Alimentary  tract  (see  Digestive  Sys- 
tem). 

Alluring  coloration,  235 

Alternation  of  generations.  256 

Amans,  417,  445 

Amber  insects,  385,  389 

Ametabola,  159 

Ammophila,  *36o,  363 

Amnion,  *i48.   149.  *i53 

Aiiiphidasis.  199 

Amphimixis,  243 

Aiuphipyra.  347 

Ampullaceum,  *9S,  96 

Anajapyx.  *6,  22 

Anal  glands.  81,  *ii7 

Anasa.  *i58 

Androconia.  *79,  80 

Anemotropism,   347 

Anergates.  336 

Angrcrcnin,  262 


Anisota,  "171 

Anisotropic,  87 

Annelids,  in  relation  to  arthropods, 
5.  *7 

Aiiomma,  335 

.Inopheles,  302,  303 

Anophthalmus,  114 

Anosia  berenice,  380  ;  plc.vippits.  an- 
tenna of,  *34  ;  dispersal,  369  ;  eclo- 
sion,  172;  so-called  mandibles,  41; 
mimicked,  ^224,  232;  pupa,  *i68  ; 
pupation,  168;  scale,  *77  ;  wing, 
*6o 

Antecoxal  piece,  *49 

Antennx,  forms  of,  +34  ;  functions  of, 
34  ;  sexual  differences  in,  *35 

Antennal  comb,  *27'o,  271  ;  neuromere, 
*46  ;   segment,   45  ;   sensilla,   94,   *9S 

Anthonomns,  397 

Anthrax,  306 

Anthrenus.   *77 

Antigeny,  35,  205 

Ant-plants,  ^272 

Ants,  castes  of,  330;  color  sense,  114; 
facets,  32 ;  general  account,  330 ; 
habits,  333  ;  harvesting  ants,  340  ; 
honey  ants,  2,36,  ^2,37:  hunting  ants, 
335:  larvae,  331;  leaf-cutting,  337, 
♦338  :  nests,  331  :  slave-making,  336 

Annrida,  development  of  mouth  parts, 
*iSi  ;  germ  band,  *iso  ;  habits,  191  ; 
pigment,   197 

Anus,  *72,  121 

Aorta,   *I2S,   *i26 

Apanfeles,  310,  *3ii 

Apatetic  colors,  234 

Apatiira.  scales,   193  ;  colors,   195 

Aphaniptera,  19,  *2i 

Aphid  ins.  310 

Aphids,  galls  of,  ^255  :  in  relation  to 
ants,  341 

Apis  mellifera,  antennal  sensilla,  *gs  ; 
cephalic  glands,  122  ;  comb,  *222  ; 
control  of  sex,  327 ;  determination 
of  caste,  327 ;  foot,  *S4 ;  general 
account,  321  ;  hair,  *269  ;  larvse, 
*324 ;  legs,  +270  :  mandible,  +38 ; 
mimicry,  225  :  modifications  in  rela- 
tion  to   flowers,   *27o,    271  ;   moults, 


467 


468 


165  ;  mouth  parts,  *44 ;  ocellus, 
*i09,  *iio;  ovipositor,  *70  ;  repro- 
ductive system,  *i4i  ;  tongue,  *97  ; 
wax,   *83,   *322,   *323 

Apneustic,   134,   189 

Apodemes,   *so 

Apodous  larvae,  47,  55 

Apophyses,  *5o 

Aporus,  363 

Appendages,  development  of,  *i49 

Apple,  insects  of,  253 

Aptera,  8 

Apterygota,  10 

Aquatic  insects,  adaptations  of,  184; 
food,  184;  locomotion,  186;  origin, 
192  :  respiration,  188  ;  systematic  po- 
sition,  184 

Arachnida,  *2,  3 

Arctic  realm,  375 

Arista,  *34 

Aristida,  340 

Arms,  J.  M.,  410,  412,  443,  444 

Army  worm,   383 

Artemia,  243 

Arthropoda,  characters  of,  *i  ;  classes, 
2  ;  interrelationships,  5  ;  naturalness 
of  phylum,  7  ;  phylogeny,  *7 

Asclepias,  *262,  *263 

Asecodcs,  312 

Ashmead,  on  Hymenoptera  of  Hawaii, 
373 

Assembling,  102 

Atemelcs,  342,  *343 

Attn,  335,  337,  *338 

Attacus,  27 

Auditory,  hairs,  107  ;  organs,  106,  *io7 

Audouin,  416 

Aughey,  on  insectivorous  birds,  288, 
455 

Austral  region,  377 

Australian  realm,  376 

Atitonieris,  81 

Ayers,  on  abdominal  appendages,  67, 
440 

Bailey,   453 

Balancers,  58 

Baldwin,  452,  453,  459 

Ballowitz,  438 

Banks,  409,  410,  465 

Barlow,  434 

Barriers,   368 

Basch,  415,  423,  429 

Basement  membrane,  *74,  75,  *79,  *85, 

*I2I 

Basiconicum,  94,  *95 
Basidium,  ^258 

Basilarchia,  mimicry,  *224,  232  ;  pro- 
tective resemblance,  218 


Bates,  on  mimicry,  225  ;  450,  461,  462 

Batesian  mimicry,  226 

Bateson,  448,  452 

Beal,  on  food  of  robin,  285,  455 

Beddard,  447,  450,  463 

Bees,  color  sense  of,  114;  hairs,  *75 

Beetles,  sounds  of,   104 

Behavior  of  insects,  345 

Bell,  453 

Bellesme,  de,  429 

Belostoma,  digestive  system  of,  *i20  ; 
predaceous,   185,  276 

Belt,  on  leaf-cutting  ants,  338,  461 

Benacus,  *i6;  caecum,  120;  mouth 
parts,   *4i  ;  predaceous,    185 

Beneden,  van,  457 

Beneficial  insects,  395 

Benton,  on  honey  bee,  324,  325,  454, 
458 

Berlese,  on  phagocytosis,   180 

Bernard,  H.  M.,  412 

Bernard,  M.,  441 

Bertkau,  on  hermaphroditism,  143,  438 

Bessels,  437 

Bethe,   on   behavior  of  ants,   334,   460 

Bethune,  408 

Beyer,  419 

Binet,  425 

Birches,   insects  of,  252 

Birds,  insectivorous,  284,  287,  291  ; 
regulating  insect  oscillations,  289 

Bittacomorpha,  *i35,  189 

Bittacus,  *i7,  52 

Black-flies,  276 

Blackiston,  450 

Blanc,  415,  430 

Blanchard,   424,   431,  457 

Blandford,  456 

Blastoderm,   *i47 

Blastogenic  variations,  241,  243 

Blastophaga,  407 

Blatta,  muscles  of,  *86,  87 ;  respira- 
tion, *i38 

Blattidse,  11  ;  spiracles  of,  66 

Blind  insects,  33 

Blissiis  leucopterus,  distribution  of, 
382  ;  losses  through,  393  ;  food  of, 
398 

Blochmann,  440 

Blood,  corpuscles,  127;  course  of, 
*i25,  *i26  ;   function,    127 

Bluebird,  food  of,  286 

Boas,  444 

Bobretzky,  440 

Bolton,  409 

Bombus,  antenna  of,  *34 ;  general  ac- 
count, 328  :  larva,  *i62  ;  mimicry, 
*235  ;  respiration,  *i38;  taste  cup, 
*99 


469 


Bombyx    mori,    Malpighian    tubes    of, 

*I24;  mid  intestine,  *i2i  ;  cenocytes, 

*i3i  ;  silk  glands,  *84,  *85 
Bordas,  423,  431 
Boreal  region,  376 
Borgert,  422 
Bot  flies,  278 
Brachiniis,  82 
BraconidjE,  310 

Brain.  *9o.  *9i  ;   functions  of,  93 
Branchial  respiration,   190 
Brandt,   A.,  439 
Brandt,  E.,  424,  425 
Brauer,   on   classification,   9  ;   types  of 

larvK,    162;   411,   417,   437,   44^ 
Braula,  309 
Braun,   457 

Breed,  on  phagocytosis,  180 
Breitenbach,  415 
Breithaupt,  415 
Briant,  415 
Brongniart,  on   Carboniferous  insects, 

384,   387,   46s 
Brooks,  414 
Brnchophagus,  *iS9 
Brues,  458 

Brunner  von  Wattenwyl,  449 
Bugnion,  182,  443 
Bumble  bees,  general  account,  328 
Bureau  of  Entomology,  407 
Burgess,  42,  415,  418,  432 
Burmeister,  410,  411 
Bursa  copulatrix,  ^142 
Buthus,  *2,  3 
Butler,  450 

Biitschli,  424,  437,  439,  440 
Butterflies,    eclosion    of,     172;     fossil, 

*390 

Cabbage  butterfly  (see  Pieris  rapcc) 

Cseca,  gastric,  *ii6,  *ii7,  119 

Ccecilius,  *i22,  ^123 

Cfficum,  *i  19,  *i20 

Cajal,  435 

Calliphora,    compound    eyes    of,    *iix, 

*II2 

Callosamia,    antenna:,    35  ;    assembling, 

102;   cocoon,   170;   odor,  82;   sexual 

coloration,  *207 
Caloptenus ,    olfactory    organ    of,    *99  ; 

tympanal  organ,  *io7 
Caloptcry.v,     development     of,     *i53: 

sexual  coloration,  206 
Campodca,  6,  *8,  9,  22,  66,  *i62 
Candeze,  421 

Canker  worms,  as  food  of  birds,  289 
Cannon,  on  phototaxis,  351 
Canthon.  *53 
Capitate,  *34 


CarabidK,    anal    glands    of,    81,    *ii7; 

predaceous,  308 
Carabidoid  larva,  *i75 
Carabus,  alimentary  tract  of,  *ii7 
Carboniferous  insects,   384,   386 
Cardiac  valve,  *ii5,  116,  118,  119 
Cardo,  *38,  39 
Carlet,  417,  419 
Carpenter,  F.  W.,  461 
Carpenter,  G.   H.,   on   relationships,   5, 

7;  410,  413,  445,  463 
Carriere,  427,  441 
Carrion  insects,  279 
Carus,  409 
Catbird,  food  of,  285 
Caterpillar,  156;  pupation  of,  168 
Catocala,  scent  tufts  of,  54  ;  protective 

resemblance,  *2i8 
Catogenus,  antenna  of,  34 
Cattie,  425 
Caudal  gills,  190 

Cccidoniyia,  egg  of,  *i59,  160;  ovipos- 
itor, *68,  69  ;  psedogenesis,  145 
Cecidomyiidre,  galls  of,  255 
Cecropia  adenopns,  *273,  ^274 
Cccropia  moth   (see  Saiiiia) 
Centrolecithal,  *i47 
Ceramby.v,    facets    of,    32  ;    ovipositor, 

*68,  69 
Ceratina,  316 
Cerceris,  363 
Cerci,  *8,  *67,  *7i,  *7t, 
Cercopoda,  68 
Centra,  82 

Cervical  sclerites,  30 
Chseticum,  94,  *95 
Chalcididse,  27,  310 
Chapman,  442,  447 
Chelostoma,  *75 
Chemotropism,  345 
Cheshire,  on  honey  bee,   *44,   71,   272. 

322.    454,   457 
Child,  428 
Chilopoda,  *4 
Chinch  bug,  distribution  of,  382  ;•  food 

of,  398  ;  losses  through,  393 
Chionaspis.  i6\ 
Chirononius,  nervous   system   of,   *9i  ; 

pupal  eggs,  14s  ;  food,  185 
Chitin,  73 

Chlorophyll,  as  a  pigment,  195,  215 
Cholodkovsky,  412,  430,  440,  441 
Chordotonal  organs,  *io8 
Chorion,  *i46,  *i6o 
Christy,  456 
Chromosomes,   146 
Chrysalis,   157 
Chrysobothris,  integument  of,  *74 


470 


INDEX 


Chrysomelidas,  silk  glands  of,  85 

Chrysopa,  *i7;  cocoon  of.  *i6g\  lay- 
ing eggs,  *i6o;  mandibles,  *38 ; 
predaceous,  308  ;  silk  glands,  85 

Chun,  421 

Cicada,  metamorphosis  of,  *i58; 
moults,  165  ;  sound,  104 

Cicindcla,  leg  of,  *S3  ;  mandible,  *38  ; 
predaceous,  308  ;  variation  in  color- 
ation,  *2I3 

Cimbex,  repellent  glands,  81 

Circular  muscles,  *i2i 

Circulation,  *i26,  127 

Circulatory  system,  124 

Claparede,  426 

Claspers,  *7i,  *72 

Claus,  411,  421,  437 

Clavate,  *34 

Claypole,   442 

Climatal  coloration,  200 

Clisiocampa,  number  of  eggs  of,  161 

Clisodon,  268 

Cloaca,  69 

Clover,  insects  of,  252  ;  pollination  of. 
266 

Clypeus,  30,  *42 

Clytra,  embryology  of,  *i47,  *i48, 
*iS4.  *i55 

Cnemidotus,  135 

Coarctate  pupa,  168 

Coccinella,  distribution  of,  378 

Coccinellidae,  predaceous,  308 ;  silk 
glands,  85 

Cockroach,    cephalic    ganglia    of,    *<)i 
fossil,  ^387,  388  ;  mouth  parts,  *Z7 
muscles,  *56,  *86  ;  respiration,  *i38 
salivary  gland,  *i22;  spermatozoon, 
*i4i 

Cocoon,  169,  *i7o 

Coeloconicum,  94,  *95 

Cnelom  sacs,   *i54 

Coleoptera,   18,  *2o,  24 

C alias,  albinism  of,  201  ;  color  .sense, 
115:   sexual   coloration,   205,   *2o6 

Collembola,  alimentary  tract  of,  *ii5; 
defined,  10;  furcula,  68;  primitive 
condition,  22  ;  ventral  tube,  68 

Colletes,  hairs  of,  *7S 

Colon,   120 

Colopha.  gall  of,  *2SS 

Color,  effects  of  food  on,  196  ;  sources 
of,   193 

Coloration,  adaptive,  216,  234;  ch- 
matal,  200;  development  of,  210: 
effects  of  moisture  and  temperature 
on,  199  ;  seasonal,  201  :  sexual,  205  : 
variation  in,  211  ;  warning,  221 


Color   patterns,    development   of,    210; 

origin,  208 
Colors,    combination,    195  ;    pigmental, 

194  ;  structural,  193 
Color  sense,  114 
Commissures,  90,  *gi 
Complete  metamorphosis,   156 
Compound   eyes,   *3i  ;   origin  of,    114; 

physiology,     m;     structure,     *iio, 

III,    *II2 

Comstock,    A.    B.,    on   ants,    145.    331  ; 
■  410,  412 
Comstock,  J.  H.,  on  venation,  58  ;  403, 

406,    410,    412,    414,    416,    417,    435, 

445,  446 
Cone  cells,  iii,  *ii2 
Conidia,  *258 
Conidiophores,  *258 
Connold,   455 
Cook,  455 
Cooke,   454 

Cope,  on  segmentation,   28  ;   452 
Copidosoma,   311 
Copris,  spermatozoon  of,  *i4i 
Coquillett,  404 
Corbiculum,  *27o,  271 
Cordyceps,  *2S7 
Corethra,  chordotonal  organs  of,  *io8; 

imaginal  buds,  *i79,  180 
Corn  insects,  253 
Cornea,  no,  *iii,  *ii2 
Corrodentia,   11.   12 
Corydaloides,   387 
Costa,  *59 
Coste,  447 

Cotton  boll  weevil,  397 
Cotton  worm,  393 
Cowan,   455 
Coxa,  *49,  *5i,  *53 
Cremaster,   168 
Cremastogaster,  333 
Creutzburg,  432 
Cricket,  stridulation  of,  106 
Crioceris,  381 
Crop,  *ii7,  *ii8 
Crustacea,  2 
Cryptorhynchus,  381 
Crystalline  cone,   no,  in,  *ii2 
Ctcnocephahis,  19,  *2i 
Cubitus,   *59 

Cuenot,  422,  423,  431.  433 
Culcx,  antennae  of,  *36  ;  characteristics 

of,    303  ;    filariasis    transmitted    by, 

305  ;  larva,  *i88  ;  mouth  parts,  *43  ; 

respiration,  *i88,  189 
Cutaneous   respiration,    189 
Cuticula,  -/T,,  *74,  *76 
Cuticular  colors,  194 


471 


Cyaiiiris  pscudargiolus,   coloration    of, 

199;     geographical     varieties,     Z7Z'- 

melanism,  201  ;  polymorphism,*  202  ; 

sexual  coloration,  206 

Cybister,    leg    of,     *i87;     locomotion, 

186.  188 
Cyclints,  stridulation  of,  104 
Cyllenc,  metamorphosis  of,   *i56 
Cynipidze,  abdomen  of,  66  ;  galls,  *254  ; 

parthenogenesis,  145,  256 
Cyrtophyllus,  stridulation  of,  iu6 

Dahl,  417,  422,  424 

Dallinger,  on  acclimatization,  242 

Darkness,  as  affecting  pigmentation, 
197 

Darts,  *7o 

Darwin,  on  instinct,  361  ;  natural  se- 
lection, 238  ;  origin  of  species,  245  ; 
451,   453,  461 

Davenport,  on  phototaxis,  351  ;  459 

Davis,  419 

Dearborn,  on  insectivorous  birds,  287, 
289,   291,  456 

Deegener,  444 

Delage,  452 

Demoor,  417 

Denny,  on  chitin,  74  ;  on  muscles,  87  ; 
410,  414,  424 

Dermaptera,  1 1 

Dermestids,  280 

Deutocerebrum,  90,  152 

Deutoplasm,  *i46 

Development,    146 

Devonian  insects,   384,   385 

Dewitz,  417,  418,  419,  432,  435,  436, 
443,  445 

Diabrotica,  distribution  of,  380 

Diacrisia,  cocoon  of,  170 

Diaphcromcra,  *2i7 

Diastole,   128 

Dibrachys,  312 

Dichoptic,  *22 

Dickel,  on  control  of  sex,  ^,27  ;  on  fer- 
tilization,  145  ;  458 

Dictyonenra,  387 

Dietl,  424 

Digestive  system,  116  :  of  beetle,  *ii7  ; 
Bclostoma,  *i2o;  Collemljola,  *ii5: 
grasshopper,  *ii6;  histology,  *i2i  ; 
moth,  *ii9;  Myri)ieleou,  *ii8 

Digoneutic,  204 

Dimmock,  on  assembling,  103  ;  on 
mouth  parts  of  mosquito.  42.  *43  : 
415,  422,  446,  455 

Dimorphism,   202 

Diuarda,  342 


Diitcutiis,    antenna    of,    *34 ;    eyes    of, 

*3i 
Diplopoda,  *3 
Diptera,    19,    *20 ;    eyes    of,    *32;    hal- 

teres,    116;    mouth    parts,    42,    *43  ; 

origin,    24;    sounds,    103;    spiracles, 

66 
Directing  tube,  85 
Direct  metamorphosis,  157 
Diseases,    their    transmission    by    in- 
sects, 299 
Dispersal,  366  ;  centers  of,  383  ;  means 

of,  367  ;  in  North  America,  377 
Dissosteira,  protective  resemblance  of, 

219  ;  stridulation,  104 
Distant,  462 
Distribution,      former      highways      of, 

370;   geographical,   366;   geological, 

384 
Dixey,  on  evolution  of  mimicry,  233  ; 

447,   448,   450,   451 
Dogiel,  431 
Dohrn,  439 

Dolbear,  on  stridulation,  106 
Dolichopodidie,  54 
Donacia,  88,  184,  189 
Dorfmeister,  446 
Dorsal   closure,    151,   *iS4 
Dorsal  vessel,   124,  *i25 
Doyere,  436 

Drift,  insect,   191 

Drone,  *32i,  322 

Drosera,  256 

Drosophila,  egg  of,  *i59 

Dubois,  433 

Ductus  ejaculatorius,   *i40,  141,  142 

Dufour,  421,  429,  432,  433,  434,  436, 
445 

Durham,   456 

Dutrochet,  433,  436 

Dyar,  on  moults,  165 

Dynastes  Hercules,  27 ;  tityiis,  distri- 
bution of,  380 

Dytiscus,  caecum  of,  120  ;  leg  of,  *53  ; 
predaceous,  276  ;  respiration,  189 

Ecdysis,  159,  164 

Eciton,  *338  ;  eyes  of,  32  ;  habits,  276, 

331,   335 
Eckstein,   454 
Eclosion,  172 

Economic  entomologist,  398 
Ectoderm,  *i48 
Edwards,  on  /.  aja.v.  203  :  on  P.  fharos, 

204;   421 
Egg-guide,  *73 
Egg-nucleus,  *i46 


472 


Eggs,  form  of,  *i59;  number,  i6i  ; 
size,   i6o 

Eimer,  452,  459 

Ejaculatory  duct,  *i40,  141,  142 

Elaphnts.  stridulation  of,  104 

Elimination  of  unfit,  240 

Ellenia,  protective  resemblance  of,  218 

Elm,  insects  of,  252 

Elwes,  462 

Elytra,  58 

Embia,  12 

Embiidae,   11,  *i2 

Embryology,  146 

Emery,  430,  433 

Eniesa,  366 

Empis.  nervous  system  of,  *9i 

Empodium,   51 

Empitsa,  *258,  259 

Enderlein,  on  Platyptera,  13,  23,  413 

Endoskeleton,  *so 

Engelmann,  409 

Enteman,  on  habits  of  Polistcs,  330, 
36s  :  450,  458,  460 

Entoderm,  148,   154,  *I5S 

Entomophthoracese,  *258 

Environmental  variations,   242 

Ephemerida,  13,  *i4;  abdominal  seg- 
ments of,  66  ;  eyes  of,  33  ;  origin,  23 

Epicaiita,  hypermetamorphosis  of,  174, 
*I7S   _ 

Epicranium,  *2g 

Epigamic   colors,   235 

Epimeron,  48,  *49 

Epipharynx,  37 

Episternum,  48,  *49 

Epitheca,  dorsal  vessel  of,  *I2S,   *i26 

Erebus  agrippina.  27  ;  odora,  distribu- 
tion of,  367,  380 

Ergatoid,  331 

Eriocephala.  mouth  parts  of,   42 

Eristolis.  mimicry  by,  *225  ;  respira- 
tion, 189 

Eruciform  larvae,  24,  *i62,  163,  178 

Erynnis  manitoba,  distribution  of,  *377 

Escherich,  420,  438 

Ethiopian  realm,  :i-/6 

Etiolin,  215 

Etoblattina,  *387 

Eudamtts  proteus.  distribution  of,  377 

Eugereon,  388,  *389 

Euphoria,  moiith  parts  of,  38,  *268, 
269 

Euplexoptera,  1 1 

Euplaca.  colors  of,  195 

Euproctis,  352 

Euschistus,  antenna  of,  *34 

Eutermes,  320 

Euthrips,  *is 


Everes,  androconium  of,  *79 

Excrements,  120 

Exner,  on  compound  eyes,  iii,  112, 
428,  459 

Expiration,  139 

Exuvi^e,  165 

Eyes,  compound,  *3i,  no;  kinds  of, 
*3i  ;  simple,  *t,2,  *io9  ;  sexual  dif- 
ferences in,  *22, 

Fabre,  J.  H.,  on  Sphcx,  359  :  432,  457, 
459 

Fabre,  J.  L.,  429,  442 

Facets.  *3i 

Fat-body,  distribution  of,  128,  *i29; 
functions,   130  ;  structure,  *i30 

Fat-cells,   129,   *i3o 

Faunje  of  islands,  371 

Faunal  realms,  374 

Faussek,  430 

Felt,  E.  P.,  403 

Female  genitalia,   *69 

Femur,   *49,   *si,   ^53 

Fenard,   439 

Fenestrate  membrane,    in,   *ii2 

Fenger,  418 

Feniseca,  309 

Fernald,  C.  H.,  on  gypsy  moth,  253, 
402 

Fernald,  H.  T.,  412,  422 

Fertilization,  147 

Fidonia,  antennal  sensilla,  *9S,  102 

Fielde,  on  ants,  331,  Z3i,  334,  35°, 
458,  460 

Filariasis,  305 

Filiform,  *34 

Filippi's  glands,   *84 

Finlay,  456 

Finn,  on  mimicry,  230  ;  warning  col- 
oration, 222,   450 

Fire-flies,   131 

Fischer,  449 

Fishes,   insectivorous,   281 

Fitch.   403 

Flagellum,   *34 

Fleas.    19,   *2i,   278 

Fletcher,   407 

Flight,  mechanics  of,  62 

Flogel,  425 

Fluted  scale,  395,  406 

Follicles,   141,   143,  *i44 

Folsom,  413,  416 

Food,  its  effects  on  color,  196 

Food  reservoir,  118,  *ii9 

Forbes,  H.  O.,  461 

Forbes,  S.  A.,  on  corn  root  louse, 
341  ;  on  economic  entomologist, 
398  ;   food  of  Carabids,  308  ;  insec- 


INDEX 


473 


tivorous    birds,    284 ;    insectivorous 

fishes.  281  ;  insect  oscillations,  289  ; 

interactions     of     organisms,     292  ; 

404;   454,  455,  456,  457 
Forbush,  on  gypsy  moth,  253,  403 
Fore  intestine,  *iis,  *ii6 
Forel,  on  ants,  331,  ^^2  ;  on  taste,  96  : 

421,  426,  427,  460 
Forficulid.-E,  1 1 

Formative  cells,  *76,  78,  *79 
Formica  cxsectoidcs.  mountls  of,  332  ; 

fitsca.  330,  335,  336;  pratcnsis,  eyes 

of,  a  ;  sangiiinea.  336 
Fossil  insects,  localities  for,  384 
Fossilization,  384 
Free  pupa,   168 
French,  G.  H.,  404 
Frenulum,  58 
Frenzel,  429,  430 
Front.  *29 

Frontal  ganglion,  *9i,  ^^92 
Functional  variations,  242 
Fundament,   150 
Fungi  of  insects,  *2S7,  *258 
Furcula,  68 

Gadeau  de  Kerville,  433 

Gad  flies,  276 

Galapagos  Ids.,  Orthoptera  of,  371 

Galea,  *37,  *38,  39 

Galerita,  anal  glands  of,  82  ;  antenna, 
*34  :   sternites,  *49 

Galls,  *254 

Ganglia,  cephalic,  ^^46,  90,  *9i  ;  func- 
tions of,  93 

Ganglion,  structure  of,  92,  *93  ;  sub- 
cesophageal,  *90,  *9i  ;  supracesopha- 
geal,  *90,  *9i 

Ganglion  cells,  92,  *93 

Ganin,  on  Platygastcr.  *i76,  442;  443 

Garman,  445 

Gastric  caeca,  *ii6,  *ii7,   119 

Gastropacha,  larval  coloration,  198  ; 
stinging  hair,  *8i 

Gastrophilns.  278 

Gastrulation,  *i48 

Gehuchten,  van,  on  digestion,  119; 
424,  430 

Geise,  415 

Gens,  30 

Geniculate,  *34 

Genitalia,  68 ;  of  female,  *69 :  grass- 
hopper, *73  :  male.  *7i  ;  moth,  *72 

Geographical,  distribution,  366  ;  va- 
rieties, 373 

Geological    distribution,    384 

Geometridae,  legs  of  larvre  of.  55 

Geotropism,  348 

Gerephemera,  386 


Germ  band,  *i47,  *i48:  types  of.  151 

Germ  cells.  146 

Germinal  vesicle,  146 

Gerris,  *i85  ;  locomotion  of,   188 

Gerstacker,  434 

Gibson,  454 

Gill.  T..  461 

Gillette,  405 

Gills,  *i34,  *I3S,  *i90 

Gilson,  430,  436,  437,  446 

Girault,  on   numbers  of  eggs,    161 

Gizzard.    118 

Glaciation.   its   effects   on   distribution, 

370 
Glands,     80;     accessory.     *i4o.     *i4i, 

*i42  ;    alluring,    82  ;    repellent.    81  ; 

salivary,    121,    *i22:    silk.    83,    *84 ; 

wax,  *83 
Glandular  hairs,  *8o,  *8i 
Glossa,  *37,  *39 
Glossina,  276,  306 
Glover.  406 
Goddard,  420 
Golgi,  on  malaria.   301 
Goliathiis,  endoskeleton  of,  *so 
Gonapophyses,  *69 
Gongylus,  235 
Gonin.   444 
Goossens,  419,  422 
Goss,   465 
Gosse.  419 
Gottsche.   426 
Gould,  447 
Graber,    on    chordotonal    organ,    *io8  ; 

halteres,    116;    hearing.    *io7  ;    410. 

417,    418,    419,    420,    426,    427.    43.1, 

440.   441.   4Sq 
Grasshopper,  alimentary  tract  of.  *i  16  ; 

genitalia.  *73  ;  hearing,  *io7 
Grassi,  on  Tcniics.  317.  318;  411,  456, 

458 
Gregson.  on  coloration.   196 
Grenacher,  on  the  compound  eye,  iii, 

114,  427 
Grobben,  412 
Gross.  439 
Growth.  164 
Grub.   157 
Grube.  433 
Griinberg,  439 
Gryllidae,   11 
Gryllotalpa,  leg  of.  *53  :  maternal  care, 

31S 
GryUus,    sense    hairs.    *ioi  ;    stridula- 

tion.   106 
Gula.   30.   39 

Gulick,  on  isolation.  249.  453 
Gypsy  moth   (see  Porthetria). 


474 


Gyrinidje,  eyes  of,  *3i 
Gyriiius,  locomotion   of,    i88;   respira- 
tion, 189;  tracheal  gills,   135 

Haase,  411,  412,  419,  435,  450 

Haemolymph,  127 

Hagen,  on  Tcniics,  318  :  409,  434, 
435,   445.   446 

Hagens,   von,  419 

Hairs,  development  of,  *76  ;  functions, 
76  ;  histology,  *76  ;  modifications, 
*75.  76  ;  pollen-gathering,  *269  ;  pro- 
tective, 298  ;  tenent,  *8o 

Halisidota,  distribution  of,  379 

Haller,  435 

Halobates,  191,  366 

Halteres,  58,  116 

Hamilton,  on  holarctic  beetles,  375, 
462 

Hammond,  417,  444 

Hamuli,  58 

Hansen,  412,  413,  415 

Harpalus,  labium  of,  *39  ;  maxilla,  *38 

Harris,  402,   465 

Hart,  446 

Hartman,   461 

Hatching,  161 

Hatschek,  439 

Hauser,  on  smell,  98,  427 

Haviland,  on  termites,  320 

Hawaii,  beetles  of,  2,72  ;  Hymenop- 
tera,   373 

Hay  ward,  on  stridulation,  106 

Head,  28 ;  segmentation  of,  44,  *46 

Hearing,  106 

Heart,  *i25,  *i26 

Heath,   on    Tcnnopsis,   318:    458 

Heer,   on  fossil  insects,   385.   389,   464 

Heider,   440,   441,   444 

Heilprin,    463 

Heim,  454 

Heinemann.  433 

Heliconiid?e,  mimicry,  225 

Heliophila,  383 

Helm,  429 

Hemelytra,  58 

Hemerocampa,  parasites  of,  312 

Hemimeridas,  1 1 

Hemiinenis,  *io  ;  hypopharynx  of,  *40 

Hemiptera,  defined,  *i6:  mouth  parts, 

40,  *4i  ;  odors,  82  ;  origin,  2;^ 
Henking,  438,  440,  441 
Henneguy,  410 
Hensen,  426 
Henshaw,  409,  465 

Henslow,  on  self-adaptation,   243,  452 
Hcptagcnia,  hypopharynx,  *4o 
Hermaphroditism,    143,   *i44 


Hesse,  429 

Hessian  fly,  losses  through,  393 

Hetcrrins,  343 

Heterocera,  defined,  18 

Heterogeny,  145 

Heterometabola,    157 

Heterophaga,  21 

Heteroptera,  defined,  *i6  ;  spiracles  of, 
66 

Hcxageiiia.  13,  *i4 :  male  genitalia. 
*7x  ;  tracheal  gills,  *i34 

Hexapoda,  defined,  4 

Heymons,  412,  413,  420,  438,  442 

Hicks,  on  olfactory  pits,   loi 

HicKson,  427 

Higgins,  446 

Hilton,  423 

Hind  intestine,  *ii7,  *i20 

Histogenesis,  180 

Histolysis,  180 

Hoffbauer,  417 

Holarctic  realm,  375 

Holcaspis,  galls  of,  *254 

Holmes,  461 

Holmgren,  416,  425,  436,  439 

Holometabola,  156 

Holopneustic,  134,  188 

Holoptic,  *T,T, 

Homoptera,  defined,   16 

Honey,  326 

Honey  ants,   336,   *i27 

Honey  bee   (see  Apis  mcUifera) 

Hopkins,  A.  D.,  405 

Hopkins,  F.  G.,  on  pigments,  196, 
447.  448 

Hoplia,  sexual  coloration  of,  207 

Horn,  on  Cicindela,  214 

House  fly  (see  Musca) 

Howard,  on  Crioceris,  381  ;  economic 
entomology,  402,  407  ;  parasitism, 
312:  410.  456,  457,  458,  463,  465 

Hubbard,  on  parasitism,  313 

Huber,  on  wax,  322 

Hudson,  462 

Humboldtia,  27Z 

Hunter,  410 

Hutton,  413 

Huxley,   on   aphids,   238  ;   414,   437 

Hyaloplasm,  88 

Hyatt  and  Arms,  quoted,  22  ;  on  accel- 
eration of  development,  178;  410, 
412,  443,  444 

Hybcniia,  196 

Hydnopliytiiin,  *275 

HydrophiJus,  18,  *20,  *i85  ;  antennae, 
35  :  leg,  *i87  ;  locomotion,  186  ;  male 
genitalia.  *7i  :  respiration,  189 

Hydrotropism,  346 


INDEX 


475 


Hydrous,   tergites   of,    *48 

Hylastes,  381 

Hylobius,  glandular  hairs  of,  *8o 

Hymenoptera,  defined,  19 ;  cephalic 
glands,  122;  eyes  of  sexes,  *33  ;  in- 
ternal metamorphosis,  182  ;  month 
parts,  *44 ;  ocelli,  ^2  :  origin,  24 ; 
sounds,  103  ;  wing,  *6i 

Hypermetamorphosis,  174 

Hyperparasitism,  311,  312 

Hyphre,  259 

Hyphantria,  298 

Hypodcrma,  larva  of,  *i62;  Uncata. 
habits   of,  278  ;    losses  through,   394 

Hypodermal  colors.    194 

Hypodermis,  ^74,  75,  *y6,  *79 

Hypognathous,  11 

Hypopharynx,  *i7,  39,  *43 

Icerya,  406 

Ichneumonids,  310 

Ihering,  von,  419 

Ileum,.  *i2o 

Imaginal  buds,   *i79,  *i8o 

Imago,   156 

Incomplete  metamorphosis,  157 

Indirect  metamorphosis,  *is6 

Ingenitzky,  438 

Inheritance  of  acquired  characters,  243 

Injuries,  transmission  of,  241 

Injurious    insects,     393  ;     introduction 

of,  397 
Ino,  antennal  sensilla  of,  *95 
Inquilines,  256,  320 
Insecta,  defined,  4 
Insectivorous   birds,   284  ;   fishes,   281  : 

plants,  256  ;  vertebrates,  280 
Inspiration,   139 
Instar,   159 
Instinct,  356  ;   apparent  rationality  of, 

357:  basis   of,  357;  flexibility,   360: 

inflexibility,  359  ;  modifications,  358  : 

origin,    361;    stimuli,    357;    and   tro- 

pisms,  361 
Integument,  73 
Intelligence,  362 
Interactions  of  organisms,  292 
Intercalary,  appendages,   *iso  ;  neuro- 

mere,  *46  ;  segment,  45 
Interglacial  beetles,  391 
Interrelations,     of     insects,     307  :     of 

orders,    21 
Intima,  *85,  *i2i,  *i37 
Iphiclidcs  ajax,  polymorphism  of,  202 
Iridescence,    193 
Iris  pigment,  *i09,  *iii 
Iris  "versicolor,  *26o,  *26i 
Irritants,  298 


Isaria,  258 

Ischnoptera,  moutli  parts  of,  *37 

Isia,   cocoon   of,    170;    hairs,    76,    167; 

moults,  165 
Island  faunae,  371 
Isolation,  249,  374 
Isoptera,   11 
IsosODia,  31 1 
Isotropic,  87 
Ithomiina:,  mimicry,  225,  226 

Jacobi,  463 

James,  W.,  459 

Janet,  on  Lepisniina,  *344 ;  muscles, 
86,  *87;  416,  420.  421,  424,  45S 

Japyx,  9,  22  ;  spiracles  of,  66 

Jaworovski,  431 

Jennings,  460 

Judd,  on  food  of  bluebird,  287  :  mim- 
icry, 232  ;  protective  adaptations, 
297 ;  protective  resemblance,  221  ; 
warning   coloration,    222;    451,    456 

Jurassic  insects,  385,  389 

Kalliiua,  protective  resemblance  of, 
216 

Kanthack,  456 

Karsten,  421 

Kathariner,  460 

Katydid,  stridulation  of,  106 

Kellogg,  on  Mallophaga,  277  ;  mouth 
parts,  42  ;  phototropism,  354  ;  pili- 
fers,  *42 ;  scales,  78,  193;  swarm- 
ing, 327;  410,  414,  416,  417.  422. 
448,  453,  460 

Kenyon,  412,  425 

Kidney  tubes,   123,  *i24 

Kingsley,  on  Arthropoda,  7,  411,  412 

Kirby,  410,  41 1 

Kirkland,   456 

Klemensiewicz,  422 

Kluge,  438 

Kniippel,  430 

Koch,  on  malaria.  302 

Kochi,  416 

Koestler,  425 

Kolbe,  410 

Kolliker,  424,  437 

Korotnel'f,  440 

Korschelt,  438,  441,  444 

Koschewnikoff,  438 

Kowalevsky,  430,  432,  439,  443 

Kraatz,  419 

Kraepelin,  415,  418 

Krancher,  435 

Krause's   membrane,    *87,   88 

Krukenberg,    on    chitin,    74  :    429,    447 

Kulagin,  42,  416,  442,  444 


476 


Labella,  *43 

Labial,  neuromere,   *46,   92,   152  ;  seg- 
ment, 45 
Labium,  30,  *3,7,  *39.  *43 
Labrum,  30,  36,  *Z7,  *4^ 
Lacaze-Duthiers,  418 
Lachnosterna,  antenna  of,  *34  ;  cocoon, 

169  :  larva,  *i62 
Lacinia,  *Z7,  *38,  39 
Lagoa.  legs  of,  55  ;  stinging  hairs,  *8i 
Lamarck,  on  instinct,  361 
Lameere,  444 
Lamellate,  *34 
Landois,  421,  426,  431,  432,  434,  437, 

442,  446 
Lang,  414 
Langer,  416 

Langley.   on  luminosity,    132 
Lankester,  411,  413,  432 
Larvce,  156  ;  adaptations  of,   165  ;  legs, 
55:    nutrition,    166;    parasitic,    314; 
types,  162 
Lasius,    age   of,    330  ;    nest,    333  ;    par- 
thenogenesis,  145 
Laveran,  on  malaria,  301 
Leachia,  eyes  of,  *3i 
Leaping,  57 
Le  Baron,  404 
Le   Conte,   461 
Lee,  on  halteres,   116,  427 
Legs,   adaptations   of,   51,   ^53  :   larval, 
55  :    mechanics,    *55,    56  ;    muscles, 
*S6  ;  segments,  *5i 
Lendenfeld,  von,  417,  424 
Lens,  *io9 

Lepidocyrtus,  scales  of,  ~y 
Lepidoptera,      defined,      17;      internal 
metamorphosis,    *i82  ;    moults.    165; 
mouth    parts,    41,    ^42;    origin,    24: 
reproductive  organs,  *i4o,  *i42  ;  silk 
glands,  *84  ;  spiracles,  66 
Lepidotic  acid,   196 
Lepisma,  *8,  9,  22,  *i62:  spiracles  of, 

66 
Lepismina  and  ants.  *344 
Leptitiotarsa,    color    pattern    of.     195, 
208,    *2i2;    distribution,    379,    382; 
dorsal  wall,   *i54  :   entoderm,    *i55  : 
folding   of   wing,    *62 :    spread,    382, 
398  :  variation  in  coloration,  *2i2 
Leptocoris,  382 
Lerenia,  ocellus  of,  32 
Leuckart.  439 

Leucocytes,  *i25,   127,   131,   180 
Leydig,   414.   421,   424,   425,    429.    431, 

437.  438,  441 
Libclliila.  13.  *i5,  *i62 


Lice,  biting,  12,  *i3,  277  ;  sucking,  16, 
*i7,  277 

Life  zones,  376 

Light,  its  effects  on  pigments,  197 

Ligula,  *39 

Liinacodes.  scale  of,   *77 

Liua  (see  Mclasoma) 

Linden,   von,   449,   450 

Lingua,  *40 

Linnaeus,  on  orders  of  insects,  8 

Lintner,  403,  465 

Lithomantis,  387,  *388 

Locality  studies,  362,  *363 

Locustidse.    1 1  ;    ovipositor,   *69  ;    sper- 
matozoon, *i4i 

Locy,  430 

Loeb,  on  tropisms,  346,  347,  349,  351, 
352,   356,  459.   460,   461 

Loew,   436 

Lomechusa,  *342 

Longitudinal   muscles,  *i2i 

Losses  through  insects,  393 

Low,  on  malaria,  303 

Lowne,  414,  426,  427,  428.  438 

Lubbock,   on  ants,   330,  331,   334,   336, 
340,    341,    350 ;    larval    characters, 
167;  muscles,  86;  vision.   113,   114; 
411,    414,    423,    427,    428,    434,    437, 
443.   453,   457,   459 
Lncatuis.  cocoon   of.    169  :    dorsal   ves- 
sel, *i25  ;  spiracles,  *i36 
Lucilia,  349,  350 
Lugger,  405 
Luks,  424 
Luminosity,    131 
Lutz,  423 

Lycariia.  facets  of.  32 
Lycsenid  larvre,  alluring  gland  of,  83 
Lycus.  mimicked,  230,  231 
Lyonet.  on  muscles,  86,  413,  423 

Machilis.g,  22  :  abdominal  appendages, 

*67  ;    nervous    system,    *90  ;    scales, 

*77  :  spiracles,  66 
MacLeay.   416 
Macloskie,  430,  435,  445 
Madeira  Ids.,  beetles  of,  371 
Maggot.   *iS7 
Malacopoda.  defined,  *3 
Malaria,  299.  *3oo 
Male  genitalia,  *7i 
Mallock,  428 

Mallophaga,   defined.    12.   *i3:   277 
Malpighian  tubes.    123,   *i24 
Mandibles,    *37  ;    adaptations   of,   *38 ; 

Culex.  *43  ;  Lepidoptera.  *42 
Mandibular,  neuromere,   *46,  92,   152;. 

segment,  45 


477 


Mandibulate  mouth  parts,  36  ;  orders, 
36 

Mann,  on  Prionus,  161 

Manson,  on  filariasis,  305  ;  malaria,  302 

Mantidse,  11,  307 

Mautispa,  24 ;  metamorphosis  of, 
*i63,    164 

Maples,  insects  of,  252 

Marey,  on   wing  vibration,   63;   417 

Marine  insects,  190 

Mark,  427 

Marshall,  on  adaptive  coloration,  230, 
231.  451 

Maternal  provision,  314 

Maturation,  *i46 

Maxillae,  *37,  *38  ;  "  second,"  39 

Maxillary,  neuromere.  *46,  92,  152; 
segment,  45 

Mayer,  A.  G.,  on  color  pattern,  211  ; 
Papilio,  200 ;  scales,  78 ;  423,  449, 
451 

Mayer,  A.  M.,  on  Cnlcx,  107,  426 

Mayer,  P.,  411,  426 

May  fly,  male  genitalia  of,  *7i  ;  wing, 
*6i 

McCook,  on  habits  of  ants,  332,  336, 
339.  340,  457 

Meconium,  172 

Mecoptera,  defined,  *i7;  origin,  24 

Media,  *S9 

Median  segment,  46,  66 

Meek,  416 

Megachile,  hairs  of.  *75 

Megalodacne,  antenna  of,  *34 

Mcgancura,  388 

Megilla,  378 

Meinert,  415 

Melander,  458 

Melanism,  201 

Mclanoplus,  alimentary  tract  of,  *ii6; 
facets,  *3i  ;  genitalia,  *73  ;  mandi- 
ble, *38  ;  respiration,  139;  skull,  *29 

Melanotus,  larva  of,  *i62 

Melasoma,  color  changes  of,  215  ;  dis- 
tribution, 378;  germ  band,  *i49 ; 
glands,  82 

Meldola,  450 

Melnikow,  439 

Meloe,  antenna  of,  35  ;  hypermetamor- 
phosis,  174 

Melolontha,  male  reproductive  system, 
*i4o;  olfactory  pits,  loi 

Menopon,  12,  *i3 

Mentum,  *37,  *3g 

Merkel,  423 

Meron,  51,  *52 

Merriam,  on  life  zones,  376  ;  462,  463 

Merrifield,  447,  448 


Mesenchyme,  *i55 

Mesenteron,  *ii5,  *ii6,  *ii7,  *ii8, 
155 

Mesoderm,  148,  *iS4 

Meso-entoderm,  *i48 

Mesothorax,  46 

Metabola,  159 

Metamorphosis,  defined,  156;  external, 
156;  internal,  179;  kinds,  23;  sig- 
nificance,   177;   systematic  value,   23 

Metatarsus,  *27o 

Mctathorax,  46 

Metcalf,  453 

Metschnikoff,  430,  439,  443 

Meyer,  G.  H.,  439 

Meyer,  H.,  432 

Miall,  on  chitin,  74  ;  muscles,  87  ;  410, 
412,  414,  424,   436.   444.  445,   446 

Miastor,  paedogenesis  of,  *I4S 

Michels,  425 

Microcentnim,  stridulation  of,  104, 
*io5 

Microptcryx,  mouth  parts  of,  42 

Micropyle,  147,  160 

Mid  intestine,  *ii7,  *ii9 

Milkweed,  pollination  of,  *262 

Mimicry,  224  ;  evolution  of,  233 

Minot,  414,  422 

Miocene  insects,  385,  390 

Moisture,  its  effects  on  coloration,  199 

Molanna,  17,  *i8 

Moles,  insectivorous,  280 

Moller,  on  leaf-cutting  ants,  338,  454 

Mollock,  on  vision,  113 

Moniez,  445 

Moniliform,  *34 

Mononychus,  268 

Mordella,  facets  of,  32 

Morgan,  C.  Lloyd,  on  food  of  birds, 
232  ;   452,   453,   459,   460 

Morgan,  T.    H.,  453,  460 

Morpho,  scales  of,  78,  193 

Moseley,  431 

Mosquito,  antenna  of,  35,  *36  ;  hear- 
ing, 107;  locomotion  of  larvae,  187; 
in  relation  to  malaria,  299  ;  mouth 
parts,  *43  :  respiration,  *i88,  189 

Moulting,   164 

Moults,  number  of,  165 

Mouth  parts,  dipterous,  42,  *43  ; 
hemipterous,  40,  *4i  ;  hymenopte- 
rous,  *44 ;  lepidopterous,  41,  *42  : 
mandibulate,  36,  *37  ;  orthopterous, 
*37  ;  suctorial,  40 

Miiller,  F.,  on  mimicry,  227  ;  wings, 
57 ;   411,   421,   442,   450 

Miiller,  H.,  453 

Miillerian  mimicry,  226,  227 


478 


Miiller,   J.,   "mosaic"   theory   of,    iii, 

42s 
Murgantia,  spread  of,  382 
Murray,  461 
Musca,   egg   of,    *i59  ;    facets   of,    32; 

fungus  of,  *258  ;  moults,  165  ;  ovum, 

*i46;   in   relation   to   typhoid   fever, 

305 
Muscidse,  cardiac  valve  of,  *w):  ima- 

ginal  buds  of,  *i79,  181 
Muscles,     circular     and     longitudinal, 

*i2i  :  of  cockroach,  *s6,  *86  :  of  leg, 

*55.     *S6 ;    number,    85  ;     structure, 

♦87  :  of  wing,  64,  *65 
Muscular,  power,  88:  system,  8s 
Mutation   theory,   247  ;   versus   natural 

selection,  249 
Mutilla,  stridulation  of,  104 
Myriopoda,   the  term,   5 
Myrmecocystus,  *337 
Myrmecodia,  27^ 
Myrmecophana.  mimicry  by,  *229 
Myrmecophilism,   340 
Myrmcdonia.  343 
Myniideon,  digestive  system  of.  *ii8  ; 

predaceous,  308  ;  silk  glands,  85 
Myrmica,  *343 
Mystacidcs.  androconia  of,  80 

Nagel,  428 

Nassonow,  438 

Natural  selection,  238 

Nearctic  realm,  375 

Necrophonts,  280,  314 

Needham,  on  digestion,  119;  venation, 

58;    417,   431,    446,   455 
Ncmobiiis,  leg  of,  *53 
Neotropical  realm,  375 
Ncpa,  respiration  of,  189 
Nerves,   of  head,   *9i  ;   structure,   *93 
Nervous   system,   89  ;   development   of, 

151,  *i54,  *iS5 
Nervures,  58 

Neuration,  58,  *S9,  *6o,  *6i 
Neurilemma,  *93 
Neuroblasts,  *i54 
Neuromeres,  defined,  45.  152:  of  head, 

♦46,  90 
Neuroptera,     defined,      16;     metamor- 
phosis of,  24,  *i63 
Newbigin,  449,  451 
Newport,      on      metamorphosis,      183  ; 

muscles,    86;    414,    423,    424,    431, 

433,  434 
Newton,  425 

Notolophus,  olfactory  organs  of,   102 
Notonecta,  *i85  ;  locomotion  of,  *i86; 

respiration,  189 


Notum,  47 

Novius.  314,  395.  406 
Nucleolus.    146 
Number  of  insects,  27 
Nusbaum,  437,  441 
Nuttall,  456 
Nymph,  159 

Oaks,  insects  of,  252 

Oberca.  eyes  of,  31 

Obtect  pupa,  167,  *i68 

Occipital  foramen,  *30 

Occiput,  30 

Ocelli,  *32  ;  structure  of,  *i09  ;  vision 
by,  109 

Ockler,  417 

Ocular,   neuromere,   *46  ;   segment,   45 

Odonata,  abdominal  segments  of,  66  ; 
copulation  of,  71;  defined,  13; 
ocelli,  32  ;  origin,  23  ;  spiracles.  66 

Odors,  82  ;  efficiency  of,  298 

Odynents,  268 

GLcanthus,  abdominal  appendages  of, 
67,  *iS2;  embryo,  *i52;  stridula- 
tion,  105 

CEcodoiiia.  337 

CEcophylla,  333 

CEdipoda,  dorsal  vessel  of,  *i25 

CEneis,  distribution  of,  370 

CEnocytes,  *i3i 

CEsophageal  commissures,  *gi 

CEsophagus,  *i  17 

CEstridje,  278 

Olfactory  organs,  98,   *99,   *ioo,   *ioi 

Oligocene  insects,  385,  389 

OUgotouia,  *i2 

Ommatidium,  no,  *ii2 

Onthophagus,  mandible  of,  *38 

OrchcUmnin,  stridulation  of,  105,  106 

Orders  of  insects,  8,  21,  *25 

Orgyia,  olfactory  organs  of,  102  ;  para- 
sites of,  312 

Oriental  realm,   376 

Origin  of  Arthropods,  *7  ;  of  insects,  6 

Orthoptera,  abdominal  segments  of, 
66  :  defined,  *io  ;  origin,  22  ;  stridu- 
lation,  104,   *io5,   106 

Osborn,   453 

Osmeterium,  *82 

Osinia.  268 

Osiiwdcnua.  cocoon  of,  169 

Osten-Sacken,  422 

Ostium,  *i25 

Oudemans,  438 

Oustalet,  434,  445 

Ovaries,  140,  *i4i,  *i42 

Ovariole,  *i43 

Oviducts,  140,  *i4i,  *i42 


479 


Ovipositor,  *69,  *7o,  *7i 
Ovogenesis,  146 

Ovum,  of  Mitsca,  *i46:  I'ancssa.  *i44 
Ox-warble,  *i62,  278,  394 

Paasch,  426 

Packard,  on  Anophthalmus.  114:  Ar- 
thropoda,  7  ;  classification,  9  :  Man- 
tissa. 24,  164;  olfactory  pits,  loi  ; 
origin  of  Coleoptera,  24 ;  relation- 
ships of  orders,  23,  24  ;  segmenta- 
tion, 28  ;  types  of  larvae,  162  ;  wings, 
57 ;  402,  405  ;  410,  411,  413,  414, 
418,  419.  4-'-^  4-'3.  4-'5.  4-28.  434. 
435.   440.    443.    444.    45 1 .   462,   465 

P.-edogenesis,  145 

Pagenstecher,  437 

Palrearctic  realm,  375 

Polccohlattina.  *38s 

Pal?eodictyoptera,  392 

Palmen,  435,  437 

Palmer,  456 

Palpifer,  *Z7~  *38,  39 

Palpiger.  *t,7,  *39 

Palpus,  *37,  *38,  *39,   *42,   *43,  *44 

Pankrath,  428 

Panorpidse,  *i7;  legs  of,  55 

Papilio,  colors  of,  200;  egg,  *i59; 
facets,  32;  head  of  pupa,  *i68  : 
melanism,  201  :  mimicry,  226,  228  ; 
osmeterium,  *82  ;  protective  resem- 
blance, 218 ;  merope.  mimicry  by, 
226,   228  ;   sexual  coloration   of.   206 

Paraglossa,  *37,  *39 

Paraponyx,  *i3S,   190 

Paraptera,  48 

Parasita,  defined,   16,  *\y 

Parasitic  insects,  lyy,  309,  314:  in 
relation  to  birds,  291 

Parasitism,  278,  309  ;  economic  im- 
portance of,  312 

Parker,  on  phototropism,  353,  460 

Parthenogenesis,  145,  256,  ^27,  331 

Passalus,  cocoon  of,  169  ;  stridulation, 
104 

Patagia,  48 

Patten,  42^,  428,  440 

Pawlovi,  425 

Pawlowa,  432 

Peckham,  on  behavior,  360,  362,  364, 
458,   460 

Pectinate,  *34 

Pedicel,  *34 

Pediculidse,  2yy 

Pediculus,  16,  *i7,  277 

Pelocoris,  leg  of.  *53 

Penis.  *7i,  *72,  142 

Pcpsis.  315 


Perez,  C,  444 

Perez,  J.,  420 

Pericardial  chamber,  *i25,    126,  *i39 

Pcripatiis.  characters  of,  *3  ;  syste- 
matic position.   5 

Pcriplaneta,  olfactory  pits  of,   loi 

Peripodal,  cavity.  181  ;  membrane. 
181  ;   sac,   181 

Pcrla.  olfactory  pits  of,  loi 

Perlidac,  12,  13,  *i4;  nymph,  *i62; 
tracheal  gills,    135 

Permian  insects,  388 

Petiolata,  21 

Pettigrew,   417 

Petunia.  *26G,  267 

Peytoureau,  420,  438 

Phagocytes,  131,  180 

Phancciis,  legs  of,  52,  *S3 

Pharynx,   117 

Phasmidae,   11,  *2i7 

Plilegethontiiis,  head  of  moth,  *42  ; 
larva,  *54  ;  moth,  *266  ;  parasitized 
larva,  311 

Pliorniia,  antenna  of,  *34  :  eyes,  *22  ; 
metamorphosis,  *i57;  phototropism, 
354 

PJwrodon,  multiplication  of,  238 

Phosphorescence,  131 

Photinns .  luminosity  of,  131,  132 

Photogenic  plate,  131 

Photopathy,  350,  351 

Photophil.  351 

Photophob.  351 

Phototaxis.  350.  351 

Phototropism,  *349 

Phragmas.  *5o 

Phthirias,  277 

Phyciodes,  coloration  of,  199,  *203, 
204 

Phylloxera,  393.  397 

Phylogeny,  5.  *7,  21,  *25,  391 

Physopoda,  13,  *i5  ;  origin  of,  2t,.   * 2$ 

Phytonomus,  legs  of,  55  ;  spread  of, 
381 

Phytophaga,  20,  *2i 

Pictet,  on  coloration,  ig6,  200 

Piepers,  451 

Pieris.  color  sense  of,  115  :  dispersion, 
366:  fat-cells,  *i3o;  imaginal  buds, 
*i8o;  olfactory  organs,  *ioi  :  scale, 
*77  ;  napi,  temperature  experiments 
on,  204  ;  protodice,  sexual  coloration 
of,  *2o6 ;  rapce,  androconium  of, 
*79  ;  developing  wing,  *i8i  ;  distri- 
bution, 381  ;  eggs,  *i6o  ;  food  plants, 
253  ;  hair,  *76  ;  larval  tissues,  *i2g  ; 
pupal    coloration,    198  :    wing   vibra- 


48o 


tion,  64  :  xanthodice,  distribution  of, 

366 
Pigmental  colors,  194 
Pigments,    of   eyes,    *iio,    *iii,    *ii2, 

*ii3;    nature    of,    195;    of    Pieridee, 

196 
Pilifers,  *42 
Pimpla,  312 
Pine,  insects  of,  252 
Pingnicula/2Z7 
Placodeum,  *9S 
Planta,  *27o 
Plants,   insectivorous,   256 ;    insects    in 

relation  to,  252 
Plasma,  127 
Plasmodium,  *30o,  301 
Plateau,  on  color  sense,   115;  muscu- 
lar   power,     88;     respiration,     139; 

416,  423,  427,  429,  432,  435,   459 
Platephemera,  *386 
Plathemis,    abdominal    appendages    of, 

*72  ;  antenna,  *34 
Platner,  434 
Platygaster,     hypermetamorphosis     of, 

167,  *i76 
Platypsyllus,  278 
Platyptera,  defined,  11,  *i2;  origin  of, 

23,  *25 
Plecoptera,    defined,    13,    *i4;    nymph, 

*i62  ;  origin,  23,  *2S 
Pleistocene   insects,   385,   391 
Pleurites,  48,  *49 
Pleuron,  47 
Plotnikow,  423 
Pocock,  412 
Podical  plate,  *73 

Podisus,  egg  of,  *iS9  ;  predaceous,  *307 
PoecilocapS'us,  color  changes  of,  215 
Pogonotnyrmcx,  340 
Polar  bodies,  ^146 
Poletajeff,   N.,  424 
Poletajew,  O.,  435,  445 
Poletajewa,  432 
Polistes,  behavior  of,  360,  365  ;  habi*s, 

329  ;  wing  vibration,  *64 
Polites,  on  Iris,  *267 
Pollenizers,  insect,  266 
Pollination,    259,    266 ;    of    Iris,    *26o, 

*26i  ;  milkweed,  *262  ;  orchids,  262  ; 

Yucca,  *264 
Pollinia,  *262 
Polybia,  328 
Polyergus,  336 
Polygoneutic,  204 
Polygonia,   dimorphism    of,    202 ;    egg, 

*i59 
Polymorphism,  202,  330 
Polynema,  177 


Polyphemus  (see  Telea) 

Polyphylla,  assembling  of,  103 

Polyrhachis,  333 

Pompilus,  behavior  of,  360,  364 

Porthctria  dispar,  damage  by,  397  ; 
hermaphroditism,  *i44  :  tracheae, 
*i38 

Post-gense,  30 

Postscutellum,  *48 

Potato  beetle   (see  Leptinotarsa) 

Pouchet,  434,   459 

Poulton,  on  adaptive  coloration,  230, 
231,  234;  on  colors  of  larvae  and 
pups,  197,  198;  444,  447,  448,  449, 
450,  4SI 

Powell,  444 

Pratt,  444 

Predaceous  insects,  276,  *307  ;  in  rela- 
tion to  birds,  291 

Premandibular,  appendages,  *i5o;  seg- 
ment, 45 

Primitive  insects,  21,  22 

Primitive  streak,  148 

Primordial  insect,  21 

Prionus.  assembling  of,  103  ;  eggs,  161 

Proljoscis,  *42 

Procephalic  lobes,  *i49,  *i50,  *iS2 

Proctodaeum,  117,  *i20,  *i49 

Proctotrypidje,  27,  311 

Prodoxns,  266 

Prodryas,  *390 

Prognathous,   1 1 

Promcthca  (see  Callosamia) 

Pronotum,   *48 

Pronuba,  ^264,  ^265 

Propodeum,  46,  66 

Propolis,  323 

Protective,  adaptations,  297  ;  mimicry, 
*224,  233  ;  resemblance,  *2i6,  220 

Prothorax,  46 

Protocerebrum,  90,  152 

Protoplasm,   adaptive,  243 

Proventriculus,  118 

Pseudocone,  *ii2 

Pseudomyrma,  273 

Psocidae,   *i2 

Pteronarcys,  13,  *i4;  tracheal  gills  of, 
13s 

Pterygota,    10 

Ptilodactyla,  antenna  of,  *34 

Pulvillus,  51,  *54 

Punktsubstanz,  *93 

Pupae,  156,  167;  emergence  of,  171; 
protection,  169  ;  respiration,  169 

Pupal  stage,  significance  of,  177,  183 

Puparium,  168 

Pupation  of  a  caterpillar,  168 

Putnam,  on  habits  of  Bombus,  328 


48 1 


Pyloric  valve,   120 
Pyrophila,  thigmotropism  of,  347 
Pyroplwnis.  luminosity  of,  131 
Pyrrharctia  (see  Isia) 

Quaternary  insects,  391 
Qucdiiis.  343 

Queen,  honey  bee,  *32i,  322;  termite, 
*3i7 

Radius,  *59 

Radl,  460 

Radoszkowski,  419 

Ranatra,  185  ;  respiration  of,  189 

Ranke,  426 

Raschke,  435 

Rath,  von,  on  sense  hairs,  *ioi,  428 

Rathke,  434,  439 

Rationality,    apparent,    357  ;    lack    of, 

36s   • 
Realms,  faunal,  374 
Reaumur,  de,  413 
Receptaculum  seminis,  *i4i,  *i42 
Recognition  markings.  235 
Rectal  respiration,  135,  190 
Rectum,   120 

Recurrent  nerve,  *9i,  *92 
Redikorzew,  on  ocelli,  *i09,  428 
Redtenbacher,  417 
Reed,  on  yellow  fever,  304 
Rees,  van,  443 

Reichenbach,  on  ants,  145,  331 
Reid,  453 
Reinhard,  434 
Relationships,  of  arthropods,  s,  *7  ;  of 

orders,   21,   *2S 
Repellent  glands,  81 
Replacements,   214 
Reproductive  system,  140 
Respiration,    137,   169 
Respiratory  system,  *i33 
Retina,  *i09 

Retinula,  109,  *iio,  iii,  *ii2 
Reuter,  428 

Rhabdom,   109,  *iio,  iii,  *ii2 
Rheotropism,  347 
Rhipiplwnis,  174,   176 
Rhopalocera.   18 
Rhyphus.  *6o 
Riley,    on    hypermetamorphoses,    174; 

losses    through    insects,     393,     394 ; 

multiplication    of    hop    aphid,    238  ; 

pollination  of  Yucca,  264  ;  pupation, 

168;   404,   405.   406;   443,   454 
Ritter,  438,  441 
Robertson,  454 
Robin,  food  of,  284 

32 


Rocky  Mountain  locust ;  dispersion  of, 

366  ;  as  food  of  birds,  288 
Rollet,  424 
Romanes,    on    instinct,    361  ;    isolation, 

249,  250,  251  ;   452,  459 
Ross,  on  malaria,  302,  303,  456 
Rossig,    455 

Rostrimi,  40 
Roaitcs.  *339 
Ruland,  428 

Sadones,   436,   446 

Saliva  of  Dytiscus.  123  ;  mosquito,  123 

Salivary  glands,  121,  *i22,  *i23 

Sambon,   on  malaria,    303 

Saiiiia  cecropia,  antennae  of,  *3S  ; 
cocoon,  *i7o  ;  egg,  160  ;  food  plants, 
253;  genitalia,  *72  ;  head  of  larva, 
*84  ;  Malpighian  tubes,  *i24;  ocelli, 
*T,2  :  odor,  82  ;  scales,  *78 

Sanderson,   466 

Sandias.   458 

San  Jose  scale,  397 

Sanninoidea,  sexual  coloration  of,  206 

Sarcolemma,   *87 

Sarcophaga,  nervous  system  of,  *gi 

Saturnia,  hairs  of,   *y6 

Saunders,  E.,  421 

Saunders,  \V.,  407,  465 

Saville-Kent,   463 

Scales,  arrangement  of,  *78  ;  develop- 
ment, 78,  *79  ;  form,  *7-,  78  :  occur- 
rence, 77  ;  uses.  79 

Scape,  *34 

Scarabseidoid  larva,   175 

Scavenger  insects,  279 

Schaffer,  on  scales,  78  ;  414,  422,  432. 
433 

Schaum,  415,  418 

Scheiber,  431.  434 

Schenk.  on  sensilla,  94,  *95,  102,  429 

Schewiakoff,  424 

Schiemenz,  430 

Schimper,  454 

Schindler,  429 

Schistocerca,  distribution  of,  367,  383  ; 
of    Galapagos    ids.,    371  :    isolation, 

250,  374 
Schiaoneura.  wax  of,  83 

Schiziira,    protective    resemblance    of, 

*2I9 

Schmankewitsch.  on  Artcmia,  243 
Schmidt,  O.,  426 
Schmidt,  P.,  412,  433 
Schmidt-Schwedt,  435 
Schneider,  A.,  430,  437,  440 
Schneider,  R.,  422 
Schultze,  426,  433 


482 


Schwarz,    on    distribution,    378,    380  ; 

myrmecophilism,   343  :   462 
Schwedt,  445 
Sclerite,  29 
Scolopendra,  *4 
ScolopendreUa,  *6,  22 
Scudder,  on  albinism,  201  ;  coloration. 

210;    fossil    insects,    385,    386,    390, 

391,  392  ;   glaciation,  370  ;   mimicry, 

227  ;   Orthoptera  of  Galapagos    Ids., 

371,    374;    spread   of  P.   rapcc,   3S1  ; 

stridulation,     106;     409,     418,     421, 

422.   426,   446,   462,   464.   465 
Scutellum,  *48 
Scutum,  *48 
Seasonal  coloration,  201 
Second  maxillae,  the  term,  39 
Sedgwick.  412 
Segmentation,  of  arthropods,  27  ;  germ 

band,    *i49,    *iSo,    *i52:    head.    44, 

*46 
Segments  of  abdomen,  65,  66 
Seitz,   447,  454,  458,  459,   462 
Sematic  colors,  234 
Seminal,   ducts,   *i40,    141  ;   receptacle, 

*i4i,  *i42;  vesicle,  *I40,  142 
Semon,  463 

Semper,  C,  on  scales,   78.  421 
Semper,   K.,   461 
Sempers,  465 
Sense  organs,  94 
Sensilla,  94,  *95 
Serosa,  *i48,  149,  *i53 
Sessiliventres,  20,  *2\ 
Setaceous,  ^34 
Setje,   modifications   of.    76 
Seventeen-year      locust,      number      of 

moults,  165 
Sexual  coloration,  205 
Sharp,  on  Atta,  335  ;  Hawaiian  beetles, 

372;  metamorphosis,   177:  410,  412. 

419,  435,  445 
Sheath.  *7o 
Shelford,  451 
Siebold,  von,  426,  436 
Silk,   8s 

Silk  glands,  83,  *84,  *85 
Silkworm  (see  Bomhyx  mori) 
Silpha,  distribution  of,  379 
Silurian  insects,  *385 
Silvestri,  on  Anajapy.v ,  *6 
Simmermacher,  422 
Siinnliinn,   276  ;   respiration,   *i90 
Sinclair,  412 
Siphonaptera,    19.    *2i  :   origin   of,    24. 

*25 
Sirex,  ovipositor  of,  *70 
Sirodot,  421,  429 


Sitaris.   174 

Size  of  insects,  27 

Skin,  73 

Skull,  *29 

Skunk,  insectivorous,  280 

Slingerland,  on  losses  through  insects, 

394;   403,   405 
Smell,   98;    end-organs   of,    *99.    *ioo, 

*IOI 

Siuiufluirus,  *9,  10 

Smith.  J.  B.,  405,  415,  416,  465 

Smith,  T.,  on  Texas  fever,  306 

Snodgrass,  on  Orthoptera  of  Galapa- 
gos Ids.,  371,  374 

Snow  flea,  *9 

Soldier,  ants,  330  ;  termites,   *3i6 

Sollmann,   418 

Somatic  cells,  146 

Somatogenic  variations,   241 

Sorensen,  413 

Sounds,   103 

Species,  origin  of,  245 

Spence,  410,  411 

Spencer,  452 

Spermatheca.  *i4i.  *i42 

Spermatogenesis,    146 

Spermatophores,  142 

Spermatozoa.  *i4i,  142 

Sperm-nucleus,  *i46 

Speyer,   on  hermaphroditism,    143 

Sphecina,  315 

Sphecius,  315 

Sphex,  *263  ;  behavior  of,  359.  362, 
*363 

Sphingidse.  as  pollenizers,  262,  *266 

Sphinx,  alimentary  tract  of,  *ii9  :  dis- 
persal, 367  ;  pulsations  of  heart, 
128;  transformation,  *i82 

Spichardt.  437 

Spines,  76 

Spinneret,  *84 

Spiracles,  closure  of,  *i36;  number, 
66,  136 

Spirobolus,  *3,  4 

Spongioplasm,  87 

Sporotrichum,  259 

Spuler,  on  scales,  78;  417,  423,  448 

Spur,  *S3 

Squama,  58 

Squash  bug.  metamorphosis  of,  *i58 

Stadium,   159 

Staginoiiiaiitis,  leg  of,  *S3 

Standfuss,  temperature  experiments 
of,   205.   373  ;   448 

Stefanowska,  on  pigment,  113,  428 

Stegoniyia.  in  relation  to  yellow  fever, 
304 

Stein,  436 


483 


of, 

456, 


Stcnaiiinia,  334 

Steitobothnis.     blood     corpuscles 

*I25  ;  stridulation  of.  104 
Sternberg,  on  malaria.  30J.  303  ; 

45- 
Sternum,  *47,  48,  *49,  66 
Stigmata  (see  Spiracles) 
Sting  of  honey  bee,  *70 
Stinging  hairs,  *8i 
Stings,  efficiency  of.  298 
Stipes.  *^7,  *38,  39 
Stokes,  436 
Stomach,  *ii9 
Stomachic  ganglion,  *g2 
Stomatogastric  nerve,  *g2 
StomodKum,  *ii6,  *ii7,  *i49 
Straton,  454 
Straus-Diirckheim,     on     muscles. 

413.  4^3 
Strength,  muscular.  88 
Stridulation.   104,  *io5,  106 
Strongylonotus.  336 
Structural  colors,   193 
Struggle  for  existence,  239 
Styloconicum.  94.  *95 
Stylops.  hypermetamorphosis  of,  i 
Subcosta,   *5g 
Subgalea,   *38 
Submentum,  *^7,   *3g 
Suboesophageal  ganglion,   *90,   *9i 
Suctorial  mouth  parts,  40 
Suffusion,   199 
Superlingure,  *4o.  150.  *i5i 
Superlingual,  neuromere,  *46,  92, 

segment,  45 
Supranesophageal    ganglion,    *90, 

93 
Suranal  plate,  68,  *73 
Surface  film.  187 
Suspensor.  *i43 
Suspensory  muscles.  *i25 
Swarming,  327 
Symbiosis,  343 

Sympathetic  system,  *9o,  *gi,  *g. 
Synaptera,  10 

Syrphidse,  silk  glands  of,  85 
Systole,   128 


Tabanidae,  276 

Tabaniis,  nervous  system,  *9i  ;  olfac- 
tory organ,  *ioo 

Tactile  hairs,   76,  *94,  *95,  96 

Tfenidia,   *I37 

Tarsus,  *49,  *5i,  *S3 

Taschenberg,  409 

Taste.  96  ;  end-organs  of,  *97,  *98, 
*99 

Taxis,   345 


Tegmina,  58 

TeguL-e,  48 

Tclca  polyf^hciuiis.  cocoon  of,  170; 
eclosion,  172;  larval  growth,  164; 
silk  glands,  84;  spinning,   170 

Teleas,  177 

Temperature,  its  effects  on  coloration, 
199 

Tenent  hairs,  *8o 

Tenthredinid;e.   25  ;   larval   legs   of,   55 

TctUhrcdopsis.  larva  of,  *i62 

Tentorium,  *3o 

Terebrantia,  20,  *2i 

Tergites,  *48 

Tergum,  47,  66 

Tcnnes  fiavipes.  318:  liicifugiis.  *3i6, 
317.  318  :  obesus,  *3i7 

Termites,  American  species  of,  318; 
architecture,  *3i9,  *320 ;  classes, 
*3i6:  "compass,"  319,  *32o ;  food, 
318:  mandibles,  *38  :  origin  of 
castes.  318:  (|ueen,  *3i7;  ravages, 
320    _ 

Termitidpe.  11,  12 

Termitophilism,  321 

Teniwpsis,  318 

Tertiary  insects.  385,  389 

Testes,  *i40,  141 

Texas  fever,  306 

Thalessa,  *3io 

Thanaos,  androconia  of,  80  ;   claspers, 

Thaxter,    on    Eiupiisa,    *258.    259,    454 

Thelen,  434 

Theobald,  465 

Thermotropism,   355 

Thigmotropism,   346 

Thomas,   C,  404,  405 

Thomas,  M.  B.,  on  androconia,  80,  422 

Thorax,   differentiation    of,    47  ;   parts, 

46  :   sclerites,   *47,   *48 
Thread-press,  *84,  85 
Thyridoptcryx,  number  of  eggs  of.  161 
Thysanoptera.    13,    *i5  :   origin   of.    23, 

*25 

Thysanura,  *8,  9  :  abdominal  seg- 
ments, 66  ;  primitive,  21 

Thysanuriform,  24,  *i62,  178 

Tibia,  *49,  *5i,  *Si 

Tipitia,  19,  *20 

Titanophasma,  27 

Toad,  insectivorous,  280 

Tongue,   39 

Touch,  96 

Tower,  on  color  patterns.  208  :  cuticu- 
lar  colors,  194:  distribution  of  Lep- 
tiiwtarsa.  379;  folding  of  wing,  61, 
*62  ;     integument,     *74  ;     origin     of 


484 


INDEX 


wings,    57:    structural    colors,    194; 

423,  449,  463 
Toyama,  438 
Tracheae,    development    of,    153,    *iS5  ; 

distribution,    *i32,    *i33:    structure, 

*i37 
Tracheal  gills,  *i34,  *i3S,   190 
Tracheation,  types  of,  134 
Trelease,  454 
Treuicx,  *2i 
Triassic  insects,  388 
Trichius,  268 
Trichodeum,  94,  *95 
Trichograiniua,  313 
Trichoptera,    17,    *i8  ;    origin    of,    24, 

*25  :   silk  glands,  85 
Trichopterygidffi,  size  of,  27,  311 
Trimen,     on     dispersal,     367  ;     on     P. 

inerope.  226,   228:   450,  451 
Trimerotropis,  protective   resemblance 

of,  219 
Trimorphism,   202 
Triphleps,  egg  of,  *i59 
Tritocerebrum,  91,   152 
Triungulin,    174,   *I75 
Trochanter,  *49,  *si,  *S2,  *S3 
Trochantine,   51 
Tropcra  luna,  cocoon  of,   170 
Tropical  region,  2i77 
Tropisms,  345 
Trouessart,   462 
Trouvelot,    on    cocoon-spinning,     170; 

eclosion,    172;    larval    growth,    164: 

442 
Tryphcrna,  197 
Tsetse  fly,  276 
Tutt,  463 
Typhoid  fever,  305 

Uhler,  on  distribution,  380 

Urech,  447,  448,  449 

Uric  acid,  124;  as  a  pigment,   196 

Utricularia,  257 

Uzel,  442 

Vagina,   140,  *i4i,  *i42 

Valette  St.  George,  la,  437 

Vanessa,  development  of  scales  of, 
*79  ;  head  of  butterfly,  *42  ;  antiopa, 
298 ;  phototropism,  353  ;  atalanta, 
color  change,  214 ;  car  did,  disper- 
sion, 366,  371  ;  geographical  varia- 
tion, 373  ;  polychloros,  coloration, 
200  ;  melanism,  201  ;  urticw.  colora- 
tion, 196,  200  ;  melanism,  201  ;  tem- 
perature experiments,  205 

Variation     in     coloration,     211,     *2i2, 

*2I3 


Variations,  blastogenic,  243  ;  classes 
of,  214,  241;  congenital,  243;  en- 
vironmental, 242  ;   functional,   242 

Vas  deferens,  *i40,  141 

Vayssiere,  432,  435,  445 

Vedalia  (see  Novins) 

Veins,  58 

Velum,  *27o 

Venation,  58,  *S9,  *6o,  *6i 

Ventral  sinus,   126,  *  139 

Ventral  tube,  *68 

Ventriculus,  *ii8 

Verhoeff,   418,    420,    458 

Verloren,  431 

Vernon,   450,   453 

Verson,  438 

Vertex,  30 

Verworn,    on    phototropism.    351  ;    460 

Vespa,  nests  of,  328,  ^329  ;  olfactory 
organ,  *ioo  ;  sensillum,  *9S  ;  taste 
cups,  *98  :  tongue,  *97 

Vespidje,  328 

Viallanes,  414,  425,  432,  435,  443 

Vision,  108 

Vitelline  membrane,  *i46 

Vitreous  body,  *io9 

Voeltzkow,   441 

Vogler,  435 

Volucella,  mimicry  by,  *235  ;  preda- 
ceous,  309 

Voss,  418 

Vries,  de,  mutation   theory   of,  247,  453 

Wagner,  J.,  412 

Wagner,  N.,  437 

Wahl,   444 

Walker,  445 

Walking,  56 

Wallace,  on  mimicry,  226  ;  natural  se- 
lection,  238:   450,   452,   461,   462 

Walsh,  on  losses  through  insects, 
394  :  403 

Walter,  on  mouth  parts,  42,  415 

Walton,  on  meron,  51,  417 

Warning  coloration,  221 

Wasmann,  on  myrmecophilism,  340  ; 
458,   460,    461 

Wasps,  328 

Watase,  428 

Wax,  glands,  83  ;  pincers,  *27o,  271 

Webster,  on  dispersal,  368,  378,  381, 
382 ;  losses  through  insects,  394  ; 
405  ;    451,   454,   457,   462,   463 

Wedde,  415 

Weed,  on  birds  in  relation  to  insects, 
286.   287,  289,  291,  456 

Weinland,  428 

Weismann,     on     acquired     characters. 


485 


243  :  conRcnital  variations,  243  : 
imaginal  buds,  180:  instinct,  361; 
somatogenic  variations,  241  ;  tem- 
perature experiments,  204 ;  use  and 
disuse,  242  ;  422,  439,  442,  446,  448, 
449,  451,  452,  453,  460 

West,  T.,  416 

Westwood,  on  Drachimts,  82;  410. 
411 

Wheeler,  on  harvesting  ants,  340  ; 
Malpighian  tubes,  123  ;  tropisms, 
345,  346,  348,  349,  355  ;  4i9,  43o. 
433,    441.    458.    459.    460 

White,  F.  B.,  418,  445 

White  grubs,  398 

Whitman,  460 

Whymper,  on  distribution,  366,  462 

Wielowiejski,  von,  432,  433,   438.   443 

Wilcox,  439,  455 

Wilde.  429 

Will,  F.,  on  taste,  96,  427 

Will,  L.,  437,  440 

Williams,  434,  445 

Wilson,   442 

Wings,  57  ;  folding  of.  61,  *62  ;  modifi- 


cations, 58  ;  muscles,  *65  ;  vibration, 

63,  103 
Wistinghausen,  von,  436 
Witlaczil.  422,  430.  440.  443 
Wollaston,  on  beetles  of  Madeira  Ids., 

371 
Wood,  T.  W.,  446 
Wood-Mason,  411 
Woodward,  441 
Worker,  ant,  330.  331  ;  bee,  *32i,  327, 

328  ;  termite,  *3i6,  318  ;  wasp,  329 

Xanthophyll,  as  a  pigment,  195,  215 

Xenoiieiira,  *386 

XiphidiiiDi,  stridulation  of,  105 

Yellow  fever,  304 

Yolk.  *i46,  *i47 

Young,  on   luminosity,    132 

Yucca,  pollination  of,  *264,  *265,  266 

Zaitha.    191 
Zander,  421 
Zimmermann.  432 
Zittel.  von.  413 


o<<< 


